Red: Puts enemies to sleep then eats their dreams. Occasionally gets sick from eating bad dreams.Yellow: If you sleep by it all the time, it will sometimes show you dreams it has eaten in the past.Gold: If you think that you had a good dream, but you can't remember it, a DROWZEE has probably eaten it.
Prof. Lotus' Notes: Drowsee are based off the Japanese myth of Baku, creatures that eat bad dreams. This is also mentioned in it's Fire Red Pokedex entry. The design is based off a Malayan Tapir which can have two tones on half of it's body.