double hippopotamus
When a person's face is so bloated and deformed that it's impossible to distinguish it from their ass. As it is, the ass already resembles a hippopotamus face. For the poor bastard sporting one of these, it also resembles theirs. It is a synonym with "Ed Zachary Disease".
Yikes - look at that double hippopotamus. If he ate with his ass and sat on his face, I wouldn't know the difference.