I was originally going to go with this idea for my own big bang fic, but I've got another one I think I'd rather work on for the time being. I'll save my own headcanon exploration of this idea for some other project some other time, and in the meantime leave this here in case anyone else wants a crack at it.

I've always found some of the pokédex entries pretty interesting. Specifically, I'm fond of two of kadabra's entries:

FireRed: It happened one morning - a boy with extrasensory powers awoke in bed transformed into Kadabra.

Emerald: It is rumored that a boy with psychic abilities suddenly transformed into Kadabra while he was assisting research into extrasensory powers.

Granted, lots of pokédex entries are logically ridiculous (ponyta jumping over Ayers Rock, grimer mutating thanks to x-rays from the moon, etc.), but even if it doesn't make sense it's always struck me as an interesting idea, and one I'm surprised more people haven't tried to work with.

So! Tell us about the Amazing Kadabraboy! What was he like before this mysterious transformation? How did it happen? Where is he now? Does he want to find a way to return to his original form, or is he enjoying being a pokémon more than he'd originally thought? (Did he even like pokémon before this happened to him?) Maybe he's a well-kept dark secret in the family of one of the psychic-type trainers... or not that well kept. Maybe he's even attracted the attention of the collector of some particularly rare and unusual pokémon... I could go on and on, but I'm sure you can think of other directions to take this, too!

I'd really love to see someone else's take on this. :) Have at it!