Murdered down the Rabbit Hole (a long logic puzzle)

Backstory

Disaster has struck for Leporidae throughout the fantasy realm -- a mass carrot famine has wreaked havoc upon all existences but our own. Because of this, 25 of the leading fantasy bunnies, rabbits, and hares from across the universes have banded together and traveled to Earth, setting up camp in China, the world's largest exporter of carrots. Here, they've organized into groups of five, with each group leaving at a designated time to collect carrots from wherever they can and bring them back to their stores, in hopes that they'll be able to collect enough carrots to bring back to their own universes and satisfy the needs of their people.

Unfortunately, it seems that a member of the Herbivorous Apiaceae Reconnaissance Enforcement (or H.A.R.E., for short) has gone rogue. During one of the missions yesterday, someone pushed poor old Uncle Wiggily down the rabbit hole, eliminating a member of the force. You're a private investigator, hired by the Enforcement as a whole. Your job is to determine who ruthlessly murdered the old sap.

Complications

Each Leporidae knows some information about the other Leporidae. Unfortunately, there are too many of them to ask each one individually about every single other rabbits, as time is of the essence before the killer strikes again. As such, you've had the suspects line up in alphabetical order, and you plan to interrogate them on the suspects to their immediate right and left. This should give you enough information to piece together the entire situation and discover the killer.

Unfortunately, you know that the killer will being lying to you to throw you off his/her scent. This means that some information might be contradictory to what you already know -- no matter. All you have to do is find out whose account of the previous day doesn't add up, and you've got your killer, right? You chuckle. If only it was so simple.

To make matters worse, you were on the phone with two of your suspects who witnessed the murder take place. They masked their voices, so you don't know which two of your suspects they were. All you know is that they were in the group directly after the murderer and Uncle Wiggily, and witnessed the murder as they were prepping for their departure. Sadly, the murderer caught wind of your call, and you've received an anonymous tip that he or she has threatened the lives of the two whistle-blowers. This can only mean that they'll be lying through their teeth as well.

Even further complicating things, someone has been raiding the carrot stores during the night, stealing a few carrots for his or herself. While you aren't here to investigate that, the perpetrator will still be terrified of being caught, and of course that means he or she will also be lying. If you can, catch that culprit as well, though it's not your main task.

To sum up what you know: There were five groups, each consisting of five rabbits, leaving at five different designated points in the day. The murderer was in the same group as Uncle Wiggily, and offed him during their scheduled time frame. Four people will be lying to you: the murderer, the two witnesses from the group directly after the murderer, and the carrot thief. Catch the murderer and lock him up for good, and give the carrot thief a good slap on the wrist.

Interrogations

Suspect: Br'er Rabbit      |      Mood: Surprisingly arrogant

You circle your first suspect, pacing slowly. He stands with a confident smirk on his face. "So, Br'er Rabbit," you drawl. "yes, sir?" He mocks. You stop in front of him, facing him head-on. After a good staredown, you peek all the way down the line of suspects.
"What can you tell me about the White Rabbit?" You ask. Br'er Rabbit smirks. "Well, I know he was in my group," the rabbit responds haughtily. You spit on the ground by his feet, but he's unfazed.
"How about this joker next to you -- Bugs Bunny, is it?" Br'er snickered. "Well, I know he was in a group with Ruby, which I'm sure didn't make Lola too happy."     You grimace. "Thank you for your time."

Suspect: Bugs Bunny      |      Mood: Inquisitive

"What's up, Doc?" You're greeted with as you approach your next suspect. "I ain't got time for your games," you snarl back. Bugs Bunny munches on a carrot.
You jab your thumb towards the rabbit you just interviewed. "Whaddya know about Br'er?" Bugs crunches his carrot a couple times, then swallows. "Well, he wasn't in my group, that's for sure."
You sneer. "How about this Bunnicula character?" Bugs stops and thinks. "He was in a group with two Rabbits. I'm sure of it!"
You frown. "Thank you for your time."

Suspect: Bunnicula      |      Mood: Thirsty

Pacing up to your next suspect, you're taken aback by his rather long and pointy teeth. He notices. "All the better to bite you with, my dear," he snarls, then laughs. "Just kidding. They're for carrot juice." You breathe a sigh of relief.
"Tell me somethin' about this joker on your left." Bunnicula looks to his left. "I mean my left," you correct. He looks to his right. "You mean Bugs? Yeah, he was in a group with two Rabbits. I know that for sure." You pause. "What's with this 'two rabbits' nonsense I keep hearin'?" Bunnicula explains, "Rabbits have some alpha dominance issues, so we try to keep them at either one or two per group." You nod with moderate understanding.
"Let's move on," you drawl. "How about Buster Baxter?" Bunnicula thinks for a moment. "Yes, he was in the third group to leave."
You scowl. "Thank you for your time."

Suspect: Buster Baxter      |      Mood: Youthfully oblivious

You round upon the youngster. "Hello, sir!" He announces cheerfully. You hold yourself back from shutting him up. After all, he's just a kid.
"You familiar at all with Bunnicula?" You ask. He nods back. "Sure am! And I know for a fact he was in the group directly after the White Rabbit. You smile. "Good to know."
Moving on, you ask, "How about Crusader Rabbit?" Buster giggles. "He's one of the most alpha of all the rabbits! I know he wasn't in a group with another Rabbit."
You feign a smile. "Thank you for your time."

Suspect: Crusader Rabbit      |      Mood: Unwaveringly confident, likely to a fault

"Stand at ready, sol-DIER!" You bark at the rabbit. He stands stiffly and attentively. "Good. You may relax." He breathes a sigh of relief as you prepare your questions.
"What do you know about one 'Buster Baxter'?" You inquire. "Sir, Buster Baxter was not in a group with Uncle Wiggily, sir!" The bunny barks back. You appreciate the respect.
"How about one 'Cuddles'?" You continue your interrogation. "Sir, Cuddles was in the last group of the day, sir!" The bunny responds.
You smile again, this time with undeserved confidence. "Thank you for your time."

Suspect: Cuddles      |      Mood: Grizzled

You nod at your next suspect with respect. "You look like a man who's seen some things," you note. "That I am, comrade," he sighs. "That I am."
"Let's get down to business," you offer. "Tell me about Crusader Rabbit." Cuddles nods solemnly. "That Rabbit was in my group."
"How about the Easter Bunny?" You ask, continuing on. "That Bunny was in the second group of the day," he says stoically.
You nod back at him with respect. "Thank you for your time."

Suspect: Easter Bunny      |      Mood: Devious

You approach your next suspect with caution. "Got any eggs on ya?" You prod. The bunny looks at you with shifty eyes. "Nnno. Why would I?" You spit on the ground. "No reason."
"What do you know about Cuddles?" You quickly fire off. The bunny is taken aback, but answers with haste. "I know that Cuddles was in a group with two Rabbits." You groan. Another 'two rabbits' clue.
"What about the Energizer Bunny?" You fire again. This time, he isn't caught off-guard. "He was in the fourth group of the day, for sure."
You spit on the ground again. "Thank you for your time."

Suspect: Energizer Bunny      |      Mood: Energetic

"Could you stop banging that infernal drum?" You yell over the clanging. The bunny shakes his head. "Sorry, but I just keep going and going and going." You scowl.
"What do you know about the Easter Bunny?" You yell over the racket. The Energizer Bunny yells back, "He was the only Bunny in his group!" He keeps drumming.
Covering your ears, you scream. "HOW ABOUT LOLA BUNNY?" The Energizer Bunny screams back, "SHE WAS IN MY GROUP!!!"
Fed up, you grab his drumsticks and snap them in half. "Thank you for your time."

Suspect: Lola Bunny      |      Mood: Competitive

As you approach your next suspect, you straighten your tie. "How are you doin' today, sweetheart?" She wrinkles her nose. "Ew, no thanks." You remain unfazed.
"Tell me about the Energizer Bunny." She rolls her eyes back in thought for a second. "Yeah, he was definitely in my group."
"And how about the March Hare?" You continue with no pause. She chuckles. "Well, he wasn't the only Hare in his group, I know that much!"
You smile and wink, much to her disdain. "Thank you for your time."

Suspect: March Hare      |      Mood: Maniacal

"Tea?" Your next suspect offers you as you approach. You look him up and down. "You don't have a teapot." He stares off into the distance, not noticing your comment.
You snap your fingers in his face, and he snaps back to reality. "What do you know about Lola Bunny?" The hare begins to drift off again, but you snap him back to reality. "Ah, yes. Lola. She was in the group directly after mine."
"And Max?" You prod while you still have his attention. "Max? He was in a group with two different Bunnies." The hare drifts off again. "Tea?" He offers.
You sigh. "Thank you for your time."

Suspect: Max      |      Mood: Sheepish

You approach your next suspect with caution. "What's got you down, kid?" He whimpers back. "I want my toy truck." You snap, and your assistant comes scurrying with the toy truck. "Are you happy now, kid?" The kid grins. "M-hmm."
"Tell me what you know about the March Hare," you gently prod. "He was in the only group with at least two Bunnies," he says nonchalantly while playing with his truck.
You make note of the previous while asking, "and how about Mr. Bun?" Max still plays with his truck. "He was in the only group with no Bunnies at all."
You pat the kid on the back. "Thank you for your time."

Suspect: Mr. Bun      |      Mood: Quiet

"How are you doing today, Mr. Bun?" You ask as you approach. "Good? Good. Let me ask you a few questions."
"What do you know about Max?" A silent pause goes by. "He wasn't in a group with Ruby? Interesting, interesting. And probably for the better."
"How about Mr. Whiskers?" Another silent pause. "He was in a group with two other Rabbits? I could have guessed that one by now," you grumble.
You share a final silent pause. "Thank you for your time."

Suspect: Mr. Whiskers      |      Mood: Moronic, if that counts as a mood

You peer through squinted eyes at the moronic grin on your next suspect. This is gonna be fun, you think to yourself. Time for bad cop.
Cracking your knuckles, you stare intently at Mr. Whiskers. "Tell me, boy, what do you know about Mr. Bun?" You turn away, then whip back towards him. "And don't you lie to me, boy." The boy just chuckles. "Mr. Bun was in a group with two other Rabbits!"
Groaning in frustration, you grab the bunny by his collar and yank him to where your foreheads are touching. "And what do you know about the Nesquik Bunny?" You bark. The bunny maintains his stupid grin. "He was in the first group of the day!"
You let go of the bunny's shirt in disgust. "Thank you for your time."

Suspect: Nesquik Bunny      |      Mood: Obscenely hyper

"I'm cuckoo for Nesquik!" The bunny exclaims as you approach. You squint. "Isn't it 'I'm cuckoo for Cocoa Puffs?'" The bunny shrugs. "I was just tryin' it on for size."
Shaking your head, you continue. "What do you know about Mr. Whiskers?" The Nesquik Bunny muses, "Ba-da-ba-ba-ba...I'm lovin' Nesquik! Uh, yeah, he was in my group."
Halfheartedly, you continue. "And what about Peppy Hare?" The Nesquik Bunny thinks for a second. "Nesquik! It gives you wings! Hrm...he was in a group with Uncle Wiggily."
You move on before he can try out another slogan on you. "Thank you for your time."

Suspect: Peppy Hare      |      Mood: Wise but wary

You smirk as you approach the next suspect. "Hey, Peppy! Do a barr--" He cuts you off. "Don't you freakin' say it, man. I swear to God, you better not say it."
"--el roll," you whisper under your breath. Clearing your throat, you ask in a booming voice, "What do you know about the Nesquik Bunny?" Peppy replies, "Yeah, he was in a group with two other Rabbits." You groan. "I swear, the next time I hear that, I'm gonna smack whoever said it."
"And what about Peter Cottontail?" Peppy thinks for a moment, then says, "Yeah, he was in a group with t--er, he was in a group with Br'er Rabbit."
You glare, then move on. "Thank you for your time."

Suspect: Peter Cottontail      |      Mood: Sick of answering the same darn question over and over

You approach your next suspect inquisitively. "Say, do you have any relation to Peter Rabbit?" The bunny groans. "NO, I don't." You shake your head. "No, I'm pretty sure you guys are the same." The bunny groans even louder. "For the last time, I'm NOT Peter Rabbit! Get it through your thick skull!" You fail to accept it. "Whaaaatever."
"How about Peppy Hare?" Peter spits back, "No, he's not Peter Rabbit, either." You correct him. "I mean what do you know about him, smart-alec?" He looks down, foolishly. "Oh. Well, I know he was in the second group of the day."
You nod. "And how about Playboy Bunny?" Peter thinks, then says, "I'm pretty sure he was in the fourth group of the day." You shake your head. "No, I mean is he Peter Rabbit?"
You grin as Peter glowers at you. "Thank you for your time."

Suspect: Playboy Bunny      |      Mood: Not as flirtatious as you hoped

You approach the next suspect excitedly, but are dismayed to see an actual bunny standing there. Well, at least he's a bunny with a bow tie, you reason. That's pretty cool.
"What do you know about Peter Cottontail?" You ask, clearing your throat. "Well, he was in a group with White Rabbit," the Playboy Bunny responds.
"And how about Rabbit?" You continue. "He wasn't the only Rabbit in his group," the Playboy Bunny answers.

Suspect: Rabbit      |      Mood: Obsessive-compulsive

As you approach your next suspect, he reaches out towards your neck. Defensively, you swat his arm away. "What are you doing, man!?" You exclaim in confusion. The Rabbit scratches his arm and twitched. "Your tie. It's not straight." You look down and adjust your tie. "Oh. Thanks."
As he breathes a sigh of relief, you ask, "What do you know about Playboy Bunny?" Rabbit responds, "Oh, he was in my group. A real stand-up guy, that's for sure." You frown.
"How about Rabbit of Caerbannog?" You continue. "Yes, he was in the second group. I do what I can to avoid him," Rabbit shudders. "Why? He's so cute!" You retort, but Rabbit just shakes his head.

Suspect: Rabbit of Caerbannog      |      Mood: Bloodthirsty Adorable and fluffy!

You approach your next suspect. "What a cute little rabbit!" You say as you pet him on the head. He eyes your jugular.
"Do you know anything about Rabbit?" You ask, still petting. The rabbit chomps down on your hand, leaving two distinct bite marks. "Ow!" You scream, then you study the marks. "Oh, I see. Rabbit was in a group with Bunnicula. Thanks!"
Continuing to pet the bunny, you ask, "What can you tell me about Reader Rabbit?" The bunny turns away from you, moving its head out from under your hand. "I get it, you're saying that Reader Rabbit was in the group directly after yours. Your such a helpful bunny!"
You give the rabbit one last pat on the head. "Thank you for your time."

Suspect: Reader Rabbit      |      Mood: Annoyingly educational

"Quick, four plus three!" You're greeted with as you approach the rabbit. "Spell 'sandcastle'! How many sides does an octagon have?" You spit on the ground.
Rather than answering his questions, you ask one of your own. "What do you know about the Rabbit of Caerbannog?" Reader Rabbit shudders. "Well, I know he wasn't in my group, luckily. He also wasn't in Uncle Wiggily's group."
Before he can ask any more questions, you ask another. "And what do you know about Ruby?" He smiles this time. "She was in my group! She's so nice -- and she's really smart, too!"
You spend a moment calculating. "Forty-three. S-A-N-D-C-A-S-S-E-L. Trick question, it has no sides." You smile smugly. "Thank you for your time."

Suspect: Ruby      |      Mood: Smart, attractive(?), competitive, curious, and responsible

You approach the next suspect with a smile. What an adorable little girl, you think to yourself. Time for good cop.
"Hey, sweetie," You say in a poorly masked gruff voice. "Can I get you anything?" She shakes her head. "No, I'm okay." You nod in understanding. "Well, let me ask you a couple questions. What do you know about Reader Rabbit?" She smirks. "Well, I know for sure he wasn't in a group with Br'er Rabbit or with Rabbit of Caerbannog -- he's terrified of both!"
You smile. "Thanks, that's very helpful. How about Trix Rabbit?" She smirks again. "Well, I know he wasn't the only Rabbit in his group -- he's always complaining about how some other Rabbit tries to take control!"
You smile again and awkwardly pat her on the head. "Thank you for your time."

Suspect: Trix Rabbit      |      Mood: Absolutely starving

"Hey, I heard you ask Ruby if she needs anything," your next suspect says as you approach. "Can you get me some food?" You look at the bony, pale rabbit. "I get it. You want drugs, don't you? You're one of those addicts, aren't ya?" You sneer. "I got you all figured out."
"No, I --" He starts, but you cut him off. "No drugs for you today, my friend. Now tell me what you know about Ruby." He sighs. "She was in a group with two other rabbits." You let out a grunt of frustration. "That's it!" You exclaim, as you smack him across the face. He whimpers.
"Now tell me about Uncle Wiggily!" You yell. "Okay, okay," he mumbles. "He was in a group with exactly one Rabbit."
A pang of regret hits you. You snap your fingers and your assistant comes running with a bowl of cereal. The rabbit excitedly snags it, then disappointedly mumbles, "Oh. Plain Cheerios." You smile. "You're welcome," you say, not noticing his disappointment. "Thank you for your time."

As you approach your next suspect, you spot a pile of mangled rabbit remains on the ground. "Oh, for the love of -- who put him here!?" Your assistant comes running over. "Sir, you said to arrange all the rabbits in alphabetical order!" You sigh. "No, I meant all the living -- whatever. Just...take him away so he can rest in peace."
As your assistant carries the limp body away, you grimace. "I'm sorry, old chap. Thank you for your time."

Suspect: Velveteen Rabbit      |      Mood: Velveteen, whatever that means

You approach your next suspect somberly. He stares somberly back. The two of you share a somber moment of silence together before you begin your questioning.
"What did you know about Uncle Wiggily?" You ask. The rabbit responds, "He was in the group directly before mine." You nod in understanding.
"And what about the White Rabbit?" He thinks for a moment. "Yeah, I'm positive he was in the first group of the day."
You share another somber moment of silence before you move on. "Thank you for your time."

Suspect: White Rabbit      |      Mood: Annoyingly dutiful

You pace up to your last suspect. "So, I hear your a man who enjoys a nice Rabbit Hole once in awhile." He shakes his head. "Not this one, not now, not ever. This one is far too deep." You spit on the ground.
"Tell me what you know about the Velveteen Rabbit," you snarl. The White Rabbit fumbles with his words. "Well, he...he was in the only group with at least...at least two bunnies."
Anxious to finish, you continue. Peering all the way back to the front of the line, you ask, "And what about this Br'er Rabbit character? What do you know about him?" Still fumbling, the White Rabbit responds, "He...he and I were the only...the only two babbits, I mean rabbits, in our group."
You let out a thankful sigh. "Thank you for your time."

Conclusion

After interrogating all the suspects, you walk around to face the entire line. "Well, you all did what you could to help -- or at least most of you did. A few of you were lyin' through your teeth, but that's okay. I've got you all figured out. Witnesses, don't worry. Your secret's safe with me. I know who the killer is." You pull out a pair of handcuffs, and walk over to one of the suspects, firmly cuffing his/her hands behind his/her back. "You have the right to remain silent. Anything you say can and will be held against you." The rest of the suspects let out a cheer, but you cut them off. "One of ya's cheerin' when ya shouldn't be," you say menacingly. You beckon your assistant over, and point to a suspect. "There's the carrot thief. Book him." Your assistant hurries over to that suspect and cuffs him, bringing him over to you. You smile triumphantly.

"Okay, now you can cheer."

A cheer erupts from amongst the remaining crowd.

Who was the killer, who were the witnesses, and who's been stealing the carrots?

Note: I apologize in advance if any of the logic is wrong. I checked it as best as I could, but something might have slipped through the cracks. If anyone notices anything wrong, I'll fix it as soon as I can.

• 1) Can we assume that only Leporidae with "Bunny", "Rabbit", etc. in their names are bunnies, rabbits, etc? 2) Special case: is Bunnicula a bunny? Commented Jul 29, 2015 at 17:44
• @VictorHenry, yes, that's how it works - for them to classify as a 'Rabbit' or a 'Bunny' they have to have the FULL word 'Rabbit' or 'Bunny' in their name. By that logic, Bugs Bunny is a bunny, but Bunnicula is not. Commented Jul 29, 2015 at 17:54
• Can suspects lie about their name? For example, maybe Peter Cottontail really IS Peter Rabbit... Commented Jul 29, 2015 at 18:01
• I've made a googe doc sheet for the TL;DR people: here Commented Jul 29, 2015 at 19:41
• @Nautilus sorry if I misled you - I clarified in the comments that in order for them to be classified as rabbits or bunnies, they have to have that word in their name. Therefore, "Buster Baxter" is not a rabbit, but "Reader Rabbit" is. Commented Jul 29, 2015 at 23:13

TL;DR, FINAL TABLE:

See the following spoiler only if you really really would like to spoil all of your fun in just a second:

GROUP 1:
Br'er Rabbit, White Rabbit, Peter Cottontail (thief), Mr. Whiskes and Nesquik Bunny.

GROUP 2:
Bunnicula, Rabbit, Rabbit of Caerbannog, Playboy Bunny and Mr. Bun

GROUP 3:
Buster Baxter, Bugs Bunny, Ruby, Reader Rabbit and Trix Rabbit.

GROUP 4:
Uncle Wiggily (dead), Crusader Rabbit, Easter Bunny (murderer), March Hare and Peppy Hare.

GROUP 5:
Cuddles (witness), Velveteen Rabbit, Lola Bunny, Energizer Bunny and Max (witness).

Ok, now let's see how it is in detail:

PART I - The beggining of the investigation

Let's make some facts that are clearly in the question preamble and should be obvious to everybody that read it all:

TRUTH 1:

Uncle Wiggily and the murderer are in the same group.

TRUTH 2:

The two witnesses are in the same group.

TRUTH 3:

The thief is not the murderer nor a witness.

These three are pretty obvious (so, I didn't even spoiler-protect them). But we can deduce something more from them (now it's all spoilers down from here):

TRUTH 4:

The witnesses are not in the same group as Uncle Wiggily and the murder.

TRUTH 5:

The witnesses are not in group 1.

TRUTH 6:

The murderer and Uncle Wiggily are not in group 5.

TRUTH 7:

Since the witnesses are liars, we have a group with two liars, except if the thief is also in this group, which would then make a group with three liars.

TRUTH 8:

There is two groups where everyone is telling the truth, except if the thief is in the same group as the murderer or the witnesses, which would mean that there would be three groups where everyone is telling the truth.

PART II - Catching lies

Now, let's try to start to look for contradictions:

Max says that March Hare was in the only group with two bunnies. March Hare also puts Max in a group with two bunnies. Energizer Bunny and Lola Bunny says that they grouped with each other, and they are both bunnies. But March Hare says that Lola Bunny is not in his group, which contradicts the idea that he is in the only group with two bunnies. So...

TRUTH 9:

There is at least one liar between March Hare, Max, Lola Bunny and Energizer Bunny.

Further:

Easter Bunny says that Cuddles is in a group with two rabbits. Cuddles says that Crusader Rabbit was in his group, so Crusader Rabbit would be with another rabbit in his group. This contradicts Buster Baxter, who says that Crusader Rabbit was not with some other rabbit.

So:

TRUTH 10:

At least one of Easter Bunny, Cuddles, Crusader Rabbit and Buster Baxter is a liar.

Petter Cottontail says that Playboy Bunny is in the forth group. Rabbit says that Playboy Bunny is also in his group, so Rabbit would also be in the forth group. Rabbit of Caerbannog says that Rabbit is in Bunnicula's group, so Bunnicula would also be in the forth group. Buster Baxter says that Bunnicula was in the White Rabbit's following group, and this would be the second group if Velveteen Rabbit is telling the truth. But Rabbit, Playboy Bunny and Bunnicula can't be both in the second and in the forth group so:

Thus:

TRUTH 11:

At least one of Peter Cottontail, Rabbit, Rabbit of Caerbannog, Buster Baxter and Velveteen Rabbit is a liar.

PART III - Some leporidae are telling the truth

Br'er Rabbit and White Rabbit said that each other was in his group. Playboy Bunny said that Peter Cottontail was in the same group as White Rabbit. Peppy Hare also said that Peter Cottontail was in Br'er Rabbit group.

So, let's see what we can deduce from that:

Between Br'er Rabbit and White Rabbit, either both are telling the truth or both are liars.

If Br'er Rabbit and White Rabbit are liars, at least one of Playboy Bunny and Peppy Hare is also a liar.

If only one of Playboy Bunny and Peppy Hare is telling the truth, then Br'er Rabbit and White Rabbit are liars.

But...

We can't have that all the four Br'er Rabbit, White Rabbit, Playboy Bunny and Peppy Hare are liars, because TRUTH 9 says that we have at least one more liar outside of this set, which would make then at least 5 liars (and also with TRUTHS 10 and 11, at least 6), so this is impossible. If just one of them would be telling the truth, which would give 3 liars, by TRUTH 9 we would get a forth liar and with TRUTHS 10 and 11 there would be a fifth liar, which is also impossible.

And then:

There should be at least two truthtellers between Br'er Rabbit, White Rabbit, Playboy Bunny and Peppy Hare. If only one of Playboy Bunny and Peppy Hare are liars, then Br'er Rabbit and White Rabbit also would be liars, and we would get 3 liars, which is impossible. However if Br'er Rabbit and White Rabbit are liars, at least one of Playboy Bunny and Peppy Hare would also be, which again would give at least 3 liars. So:

TRUTH 12:

Br'er Rabbit, White Rabbit, Playboy Bunny and Peppy Hare are all telling the truth.

And this also means that:

TRUTH 13:

Br'er Rabbit, White Rabbit and Peter Cottontail are all in the same group.

PART IV - A tale of two bunnies

Let's continue with inferences from the truths above:

White Rabbit says those two truths:

TRUTH 14:

Velveteen Rabbit is in a group with two other bunnies.

TRUTH 15:

There is definitively only one group with two bunnies. And no group with more than that.

Let's see those bunnies:

We have six bunnies: Bugs Bunny; Easter Bunny; Energizer Bunny; Lola Bunny; Nesquik Bunny and Playboy Bunny.

Which means that:

There are 5 groups, one of them have 2 bunnies. Since we have only 4 other bunnies and 4 other groups and no other group has 2 or more bunnies then:

TRUTH 16:

All of the groups have at least one bunny.

And finally:

TRUTH 17 (very important, so it is very spoilery, beware):

Max is a liar!

Which also implies that:

TRUTH 18:

March Hare is not in the group with two bunnies.

PART V - The secret of the bunnies

Br'er Rabbit is telling the truth, so Bugs Bunny is in the same group as Ruby. Reader Rabbit says that Ruby is in his group. Bugs Bunny says that his group is not the same as Br'er Rabbit group.

So what?

If Bugs Bunny is lying, then Br'er Rabbit, White Rabbit, Peter Cottontail, Bugs Bunny and Ruby are all in the same group. Also, Reader Rabbit would be a liar. If Reader Rabbit is a liar then Rabbit of Caerbannog would also be on his group. And then, Ruby would also be a liar. This would make all the four liars as Max, Bugs Bunny, Ruby and Reader Rabbit. However, since Bugs Bunny and Ruby are in the same group, then they would either both be witnesses or be the thief and the murderer. None of them can be the murderer because Uncle Wiggily is not in the group. However if they are the witnesses, that would make Velveteen Rabbit a liar also, which would give us 5 liars.

Thus:

TRUTH 19:

Bugs Bunny is telling the truth.

Further:

Energizer Bunny and Lola Bunny both says that they are in the same group, which would be the only group with two bunnies. Easter Bunny says that Energizer Bunny is in the forth group. Energizer Bunny and Lola Bunny says that they are with each other. Peter Cottontail says that the Playboy Bunny is in the forth group. So, if all of them are telling the truth, we would have the forth group with three bunnies (Energizer Bunny, Lola Bunny and Playboy Bunny). So:

TRUTH 20:

There is at least one subgroup of liars between Easter Bunny, Energizer Bunny and Lola Bunny, and Peter Cottontail.

Things are getting hot, huh?

If Energizer Bunny and Lola Bunny are liars, then Easter Bunny could only be in the group with two bunnies, together with Velveteen Rabbit. However, Easter Bunny says that Energizer Bunny is in the forth group and Peter Cottontail also says that the Playboy Bunny is in the forth group, which would create two groups with two bunnies. This way, Energizer Bunny, Lola Bunny, Max and one of Peter Cottontail or Easter Bunny would be our four liars. Then, Cuddles asserts that Easter Bunny is in the second group, which also puts Velveteen Rabbit in the second group, and then puts Uncle Wiggily in the first group together with Br'er Rabbit, White Rabbit, Peter Cottontail and someone else. However, Mr. Whiskers and Nesquik Bunny would also be telling the truth and they would also be in the first group together with Peppy Hare, and then the first group would have 7 members, which can't be truth. So:

TRUTH 21 (very important, so it is very spoilery, beware):

Energizer Bunny and Lola Bunny are telling the truth.

And then:

TRUTH 22:

March Hare and Peppy Hare are in the same group.

And:

TRUTH 23:

At least one of Easter Bunny and Peter Cottontail is a liar.

PART VI - Finding truthtellers

If Max is not in the same group as Energizer Bunny, Lola Bunny and Velveteen Rabbit, then March Hare is also a liar. If Velveteen Rabbit is also a liar, then by choosing the forth liar from TRUTHS 10, 11 and 23, only Easter Bunny could be the remaining liar.

This would also mean that Rabbit, Playboy Bunny and Bunnicula are in the fourth group (because Peter Cottontail, Rabbit, Rabbit of Caerbannog and Buster Baxter would not be liars) and Peppy Hare and March Hare would be in the second group.

Lola Bunny's group:

• Could not be the first (this would put three rabbits in the same group, Velveteen Rabbit, Br'er Rabbit and White Rabbit);
• Nor the second (Peppy Hare and March Hare are there, and since Nesquik Bunny would not be liying, then Uncle Wiggily and the murderer would also be there, and this group would then feature six or more members);
• Nor the third (would make March Hare not a liar);
• Nor the fourth (three rabbits and would make Easter Bunny not a liar).
• So they could only be in the fifth group. Since Max and March Hare are liars, none of them could be in the last group, otherwise they won't be lying.

Cuddles says that Easter Bunny is in the second group, which would also feature March Hare. So Velveteen Rabbit could only be the thief, Easter Bunny and March Hare would be witnesses in the second group and Max the murderer in the first group. However the first group would also feature Br'er Rabbit, White, Petter Cottontail, Nesquik Bunny and Mr. Whiskers, which would result in six members. So this all is not possible.

• Phew, that was a long and hard reasoning:

TRUTH 24:

If Max is not in the same group as Energizer Bunny, Lola Bunny and Velveteen Rabbit, then Velveteen Rabbit must be telling the truth.

Let's see to what this drive us:

So, if Max is not in same group as Energizer Bunny, Lola Bunny and Velveteen Rabbit, March Hare is a liar and Velveteen Rabbit must be telling the truth. Since March Hare would be lying, he would not be on Uncle Wiggily's group and could not be the murderer. Since Max is known to be lying, March Hare could not be a witness also. So, in this case, he would be the thief and Max would be the murderer. Peppy Hare would go in the same group as March Hare, which contradicts Nesquik Bunny, which would also be a liar. Having Max, March Hare and Nesquik Bunny as liars made we unable to choose just one more liar from TRUTHS 10, 11 and 23, we would need at least two and would get 5 liars.

Therefore, we unleash a combo of important revelations (very spoilery everything from now to the very end):

TRUTH 25:

Max is in the same group as Energizer Bunny, Lola Bunny and Velveteen Rabbit and he is a witness.

Which implies that:

TRUTH 26:

March Hare is telling the truth. He and Peppy Hare are in the same group as Uncle Wiggily.

Which also implies that:

TRUTH 27:

Velveteen Rabbit is telling the truth, because Uncle Wiggily is in the preceding group.

TRUTH 28:

Nesquik Bunny is telling the truth because Peppy Hare is in Uncle Wiggily's group.

TRUTH 29:

Mr. Bun is telling the truth, because Max is not with Ruby.

TRUTH 30:

Crusader Rabbit is telling the truth because Buster Baxter is not in the same group as Uncle Wiggily.

TRUTH 31:

Cuddles is in the last group.

What more?

If Reader Rabbit is a liar, then Rabbit of Caerbannog was in his group and would be also a liar. So, if Reader Rabbit is a liar, then Max, Rabbit of Caerbannog and Easter Bunny would be also the liars. But this would also make Ruby a fifth liar. Therefore:

TRUTH 32:

Reader Rabbit tells the truth. And he is in the same group as Bugs Bunny and Ruby, which also tells the truth.

And:

If Trix Rabbit is lying, then there was two rabbits in Uncle Wiggily's group. Also March Hare and Peppy Hare are in this group. However there would be no bunny in the group then, which would be a contradiction.

Then...

TRUTH 33:

Trix Rabbit is telling the truth.

And...

Also, if Mr. Whiskes is lying, he would be either a witness or the murderer. However, Nesquik Bunny is in the same group as him, which means that he can't be a witness in the group of Lola Bunny and Energizer Bunny. If he is the murderer, the other leporidae in the group would be Uncle Wiggily and the two hares, with no space for a rabbit.

Then:

TRUTH 34:

Mr. Whiskes is telling the truth.

TRUTH 35:

The first group is Br'er Rabbit, White Rabbit, Mr. Whiskes, Peter Cottontail and Nesquik Bunny.

PART VII - Mystery solved: The gran finale

Which rabbits goes in pairs and whoever is lonely?

• We have Br'er Rabbit and White Rabbit as a pair.
• Whoever goes with Uncle Wiggily is lone. And it is not Rabbit of Caerbannog (as attested by Reader Rabbit), nor Velveteen Rabbit (as already explained), nor Reader Rabbit (which is with Bugs Bunny and Ruby).
• We are unsure if Rabbit of Caerbannog, Velveteen Rabbit and Reader Rabbit have pairs.
• Trix Rabbit has a pair (as attested by Ruby).
• Rabbit has a pair (as attested by Playboy Bunny).
• If Buster Baxter tells the truth, then Crusader Rabbit is lone, otherwise he is not.

• But...

The only possible rabbit that left to be in Uncle Wiggily's group is...

TRUTH 36 (extremely spoilery):

Crusader Rabbit is in the group of Uncle Wiggily together with March Hare, Peppy Hare and either Easter Bunny or Playboy Bunny.

But...

Playboy Bunny, Crusader Rabbit, Peppy Hare and March Hare are all known to tell the truth. So:

TRUTH 37 (supreme spoilery):

Easter Bunny is the murderer! His group also features Crusader Rabbit, March Hare, Peppy Hare and Uncle Wiggily.

And also:

TRUTH 38:

Buster Baxter tells the truth.

TRUTH 39:

Bunnicula is in the second group with two rabbits.

And:

Velveteen Rabbit can't be in the first group, because there would not be prior group for Uncle Wiggily. He could not be in the second because this would put Uncle Wiggily in the first group, and we already know that he is not there. He can't be in the third group because this would put Uncle Wiggily in the second group, but Uncle Wiggily's group has only one rabbit and the second group has two.

So:

Uncle Wiggily is not in the second group, which also means that Peppy Hare is not either. And thus...

TRUTH 40 (very spoilery):

Peter Cottontail is a liar! He is the thief!

And finally:

Cuddles is in the last group, but Crusader Rabbit can't be there.

So...

TRUTH 41 (very spoilery):

Cuddles is a witness.

PART VIII - Completing the board

So, what are the groups afterall?

There still a few positions that are unknown, but:

TRUTH 42:

Rabbit and Rabbit of Caerbannog are also telling the truth, because we had run out of liars.

So, it is very easy to fill all them remaining positions:

TRUTH 43:

Rabbit and Rabbit of Caerbannog pairs in the second group with Bunnicula.

Further:

Since Cuddles is a witness in the fifth group, then:

TRUTH 44:

The murderer is in the forth group. So, Uncle Wiggily, March Hare, Peppy Hare, Easter Bunny and Crusader Rabbit goes there.

And also:

TRUTH 45:

The witnesses are in the fifth group. So this is the group of Cuddles, Max, Velveteen Rabbit, Lola Bunny and Energizer Bunny.

TRUTH 46:

Bugs Bunny, Ruby and Reader Rabbit must fill the third group because they wouldn't fit anywhere else.

Then:

TRUTH 47:

Playboy Bunny only fits the second group.

And:

TRUTH 48:

Trix Rabbit must pair Reader Rabbit in the third group.

And we finish with:

TRUTH 49:

Mr. Bun gets the last remaining space in the second group.

GAME OVER

Finally, the full groups table:

GROUP 1:

Br'er Rabbit, White Rabbit, Peter Cottontail (thief), Mr. Whiskes and Nesquik Bunny.

GROUP 2:

Bunnicula, Rabbit, Rabbit of Caerbannog, Playboy Bunny and Mr. Bun

GROUP 3:

Buster Baxter, Bugs Bunny, Ruby, Reader Rabbit and Trix Rabbit.

GROUP 4:

Uncle Wiggily (dead), Crusader Rabbit, Easter Bunny (murderer), March Hare and Peppy Hare.

GROUP 5:

Cuddles (witness), Velveteen Rabbit, Lola Bunny, Energizer Bunny and Max (witness).

• This looks good so far - can you put a tl;dr list of all your groups at the bottom so that I can check them easily? :) Commented Jul 30, 2015 at 14:19
• @BaileyM I did not determined all the groups, as this was not required. But I will edit this now to make it truly completed with two or three extra steps. Commented Jul 30, 2015 at 14:21
• This is perfect! Good job :D Commented Jul 30, 2015 at 14:45
• @TobyY. Edited the parts between 9 and 10. I got some long hours to develop this, and in the process I had writte and rewritte tons of text from reasoning lines that eventually lead me to dead-ends. So I had to remove, rephrase, reorder, retrace the thinking lines hundreds of times. Naturally, in such process I was very afraid that I could slip something wrong, even after many text reviews. You found my first slip with that, it was a fragment of an early reasoning that took me to nowhere. Fortunately, it was also easy to fix. Commented Jul 30, 2015 at 20:49
• This is amazing! I missed it at the time as I was away, but what an awesome long and detailed answer: +1 to you, good sir. Commented Aug 14, 2015 at 11:05