The Lava Eye is a character that appears in the episode "Incendium." Jake jumps over it while singing "All Warmed Up Inside." It is unknown whether the eye is part of a larger lava monster, since it rests in a pool of lava and merely opens its lid when Jake apparently wakes it up.
It is a giant eye. Its eyelid is red, and its pupil looks like an open mouth with sharp teeth. It also has veins branching from each corner toward the pupil.