He appears dark green with a light green back fin.
"Enchanted Tiki Dreams"
He is neon green with a light teal fin running down his back. He also has a small light brown fedora with a purple stripe on his head.
Role in series
He steals SpongeBob's ice cream cone by sliding through his holes. When SpongeBob is not assertive enough, Plankton gets inside his mouth and yells at the Electric Eel to hand over the ice cream or else "every waking moment of [his] life will be filled with pain and misery," making Eel cry and run away, throwing the ice cream at SpongeBob.
In "Walking Small," he is seen to have the power to stretch over long distances. This may have meant to be done, as eels are usually long and skinny.
In "Walking Small," he is shown to be taller than SpongeBob, but in "Enchanted Tiki Dreams," Electric Eel is a bit shorter than him, also being a brighter shade of green. He returns in "Mall Girl Pearl" with his original taller design.