Faceguy

The Faceguy is the boss of the fifth dungeon, Catfish's Face. He is a giant face that sprouts out of the wall, although due to coding errors less than half of his face appears at a time. He attacks by opening holes in the floor and launching tiles at the player. Bombs are his only weakness.

Based on in-game code and extensive forensic facial reconstruction techniques, we have managed to create an image that suggests what the entire Faceguy probably looks like: Faceguy is also the name of a Let's Player on the SomethingAwful forums, but that's neither here nor there.