This guy was SO much fun to do.
He's an enemy for Level 4: The Lava Factory, which will be the final level for the game. Essentially when you enter the Lava factory it's full of Lava, and you're forced to swim around in it with a bunch of flesh-eating (tank-eating?) Piranha. Once you've drained the Lava, evolution takes place, and instead of dealing with the sea-dwellers, you get amphibians.
This guy essentially uses his long tongue to pull you towards him. Pretty creepy.