It's just a closet.
3 seconds sound clip from the Monsters, Inc. movie soundboard.
You can hear this line at 00:32:50 in the Blu-ray version of the movie.
Quote context
[...]
- No. Hey, hey, that's my bed! You're going to get your germs all over it.
- Fine. My chair is more comfortable anyway.
- Hey, that looks like Randall. Randall's your monster.
- You think he's going to come through the closet and scare you.
- Oh, boy, how do I explain this?
[...]