It is a larger variation of a normal Krabby Patty. If the customer requests it, it can also be batter fried twice on a stick.
Role in episode
Harold orders a King-Size Ultra Krabby Supreme that was also batter-fried twice on a stick with mayonnaise at the beginning of the episode. He then proceeds to eat it and squirts the mayonnaise bottle into his mouth, which prompts Squidward to express his distain for Krabby Pattiees, beginning the episode's conflict.