In a kingdom far far away there is a castle with an irritated king. Why irritated you ask? He just came back from a trip to the western world and he was thrown out from nearly all the parties... just because he refused to do all those hard math riddles. Seriously, he felt so insulted by their insolence... yet also strangely inspired! He would right this wrong directly! As soon as he gets back in his castle he calls in his head of guards to devise a new password scheme.
A merchant comes and the guards ask him
Original version... containing a mistake... see comment on accepted answer :'( : Kind merchant, what brings you to our gates?
Kind merchant, what is it that brings you here?
The merchant closes his eyes for a bit and says
Trade and wares for our sovereign, my fair guards.
And they let him right in.
Behind the merchant a couple of spies for a neighboring nation were waiting to be let in. They had come and gone from the city many times, but they grew suspicious as the guards were behaving differently from other days and turned around to listen for awhile from far away whilst acting as if they were waiting for a bit.
A monk arrives at the gate, and the first guard says
Father, it shames us that we have to ask this of you, but what...
And the second guard continues
... brings thee here?
And the monk answers
It is quite all right my children, I have heard of this new scheme your rex has thought of. Be that as it may be, I will be here for awhile, if you need my help or advice, visit me at the monastery.
And walks right in.
A forester arrives at the gate and says
Do you really need to ask me again? I have left and entered all the time.
Yes, Yes, we do.
And the forester sighs
That king of ours... as much as I love him, sometimes... sigh
And the guards chuckle to each other and let him right in.
A beggar arrives at the gate
Don't come to our city! Not like a piece of filth like you will know our password! If you knew you would just spoil it.
The first guard exclaims. The second guard gives an irritated stare at his companion and kindly says
Well... he is half right, do you?
The beggar, doesn't even wait to think and starts answering directly
Yes of course I do... the monarch... ehm... I have heard it from our own monarchs mouth when he announced it last week. I may be cripple and without arms, but I am not an idiot!
And in he goes.
For two hours nobody turns up at the gate, before the unloved mother in law of the second guard turns up.
Welcome back, need help?
The first one says kindly, seeing she is pushing in a cart that's far too heavy for her. The lady smiles kindly at him and is about to answer when the second interjects
What brings you here to our gate at night?
The lady halts, thinks for a bit, then scowls at her daughters husband angrily before thinking for a bit longer before answering half afraid:
It is all to honour our kind and just and fair overlord of course...
And the second guard replies
You dare call our fair King an overlord?! You...
Before the first interjects and whilst helping her in through the gate says to the second guard
You ass! She did not deserve that! If you ever do something like that again I will seriously tell your wife!
At which point the second guard goes white with fear.
During the exchange one of the spies looks at the other and says
I know it! It's so simple! This sounds just like that king of theirs!
He walks up to the guards and they say
So, decided to return after all? Hiding in the trees and everything...
And the second continues with
Anything you wish to say for yourself?
The spy looks doubtful for a bit... goes silent... and then exclaims
His Majesty! His Majesty wants me in!
The guards look at each other, nod, and kill him in one move whilst the first says
You idiot, did you forget who we are?
The question is: What should the spy have done/said differently? And why?
It didn't all work out as nicely as I was hoping, because of a reason I can't disclose (should have checked better before I started). Either way, still think it's a nice simple puzzle with a nice little twist in there to keep you guys thinking for a bit :P Though who knows, maybe you will get it within minutes :P
If somebody else would have given the spies answer to the same question they would have been let in. Might have been scolded for giving a 'poor' answer, but definitely would not have been killed.