He is an olive yellow fish with dark orange fins, mustard yellow lips, and mustard yellow eyelids. He wears a white shirt.
Oswald McNulty was first mentioned by Squidward when he told Mr. Krabs that McNulty only needs to eat one patty to win.
Later, he made an appearance in a flashback where he defeated Larry, Mrs. Puff, and Sandy in a previous eating contest.
During Patrick's training, a film reel of McNulty was shown, revealing that the reason he always wins is because he never tastes the patties.
He made a real appearance during the contest. He ate faster then Patrick at first, but Patrick caught up to him. When both eaters reached 999 patties, McNulty fell backwards and lost, making Patrick the winner after he ate the last patty.