Drowzee

“Puts enemies to sleep then eats their dreams. Occasionally gets sick from eating bad dreams.”

— Pokémon Red

“If you sleep by it all the time, it will sometimes show you dreams it has eaten in the past.”

— Pokémon Yellow

“If you think that you had a good dream, but you can't remember it, a DROWZEE has probably eaten it.”

— Pokémon Gold