I think I'd prefer to stay human, thanks. But if I were made to choose some other species I think I'd go with some kind of poisonous slimy thing like a tree frog that no other animal wants to eat. I really wouldn't want to experience that. Plus I could end up as some rare and unknown species that holds the cure to cancer or whatnot. Not that I'd care on account of being a frog, but, you know, that's more than most animals can claim.