Ultra-sun: It can be spotted near recreational facilities, intending to eat the pleasant dreams of children who enjoyed themselves there that day.Moon: It finds really fun dreams tasty. When it makes friends with people, it may show them the most delicious dreams it’s ever eaten.Alpha-sapphire: If your nose becomes itchy while you are sleeping, it’s a sure sign that one of these Pokémon is standing above your pillow and trying to eat your dream through your nostrils.
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.