I met a man once while out for a walk. "Tut, tut!" He would say, as he wandered this way and that. I saw him approach a group, "You there! Will you trade? I've got a lovely a nut right here. What about you? A nut for a jar of tuna?"
I didn't think this question was sincere, because I noticed that although nobody answered, great relief and momentary joy filled his eyes. I was very confused. Finally, he came to me and I asked him, "Are you okay?"
"Me? Never been better, just been made a little crazy.." he answered.
I inquired, "Who made you crazy?"
He replied, "No! Not who, but what!"
I followed his lead, "Sir, what made you crazy?"
But he only chuckled, and said his familiar "Tut, tut!" I continued to press but all he gave me were even more tuts. His head had been in the clouds, it seemed.
Can you figure out what made the man crazy?
The answer reveals a bit of backstory for the "odd man," specifically, some place he has been. This answer is given not by something the man said, but rather by something recounted by the story teller. The comment by @msh210 is important.