The Triple Demons of Compromise are demons who always compromise on everything.
"One is short and fat, one is tall and thin and one is just like the others." The one that is just like the others is neither tall or short nor skinny or fat. He's just in the middle, so not too tall, but not too short, and not too skinny, but not too fat either. The short, fat one and the tall, thin one disagree but the middle one makes them agree. They are first seen when they are chasing Milo, Tock, and the Humbug up the Mountains of Ignorance. Jules Feiffer purposefully never illustrated these characters.