So apparently we've definitely established that in the pokemon universe: DEAD PEOPLE CAN BECOME POKEMON. They can then be crammed into pokeballs and forced to do your bidding.
I'm not kidding. Meet YAMASK.
His description in Pokemon Black:
"Each of them carries a mask that used to be its face when it was human. Sometimes they look at it and cry"
and in Pokemon White:
"These Pokémon arose from the spirits of people interred in graves in past ages. Each retains memories of its former life."
Between this and the fact that the pokemon already looks like it's crying is really amazingly creepy. ((And a little bit cool.))
It's definitely a very interesting dark element in an otherwise happy and perky game that revolves around people and their happy little animal-monster companions, although if you think about it, the concept is teetering on a dark bent already. People are sending their children out to go battle people with other animal-monsters, and capture wild, untrained ones in pokemon balls.
Realistically, you could get yourself seriously freaking hurt if you tried to tangle with a twenty foot rock snake armed with a tiny water spitting Newt or the like, but in the DS games, you merely risk getting knocked out, not getting turned into a red smear on a cave wall.
I often regale (bore) people silly by pointing out that I have actually played an pokemon game where the trainers and pokemon could get hurt, or even killed trying to catch particularly dangerous wild pokemon, but really, it was a pretty Kick-Ass roleplay. My trainer actually lost their hand being cocky and stupid, but thats what you get assuming that you're going to take on an pokemon with a blade on it's head by yourself. It really really is a fun idea and people should try it more often.