It is a larger variation of a normal Krabby Patty. It can also be batter-fried twice, or be on a stick, only if the customer requests it.
Role in episode
Incidental 40 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 disdain for Krabby Patties, beginning the episode's conflict.