rats aren't dumb
my guineapig was really limber, he was a fatass and managed to climb out of his cage. i was like omg. i saw him do it, he fell on the floor and i was so afraid he hurt himself but he was ok. but i removed the door so he could run around in my room and piss and poop everywhere.
the door was always open anyway but i was afraid he would hurt himself on it cuz it had these things poking out of it so you could put hay on the door and i was afraid he would poke his eye out.
i also built him stairs cuz his paws got stuck on the way out of the cage, i dunno why they build them like that.