Santa Claus is a character who only appears in Operation: N.A.U.G.H.T.Y. He is the only person who can withstand the negative side-effects of the Reindeer System. Santa Claus seems to be one of the few good adults in the series. He gives presents to children all over the world. The Delightful Children From Down the Lane however, have never received any presents from him, and tied him up as an act of revenge. They tried to use the power of the Reindeer System, but were too weak, which resulted in them turning into Grinch-like creatures thanks to their greed. Later, Numbuh 3 steals the Reindeer as well, believing that since she's the most generous person in the world, she deserves all the presents in the world. This results in her becoming a Grinch as well. Santa sends Numbuh 4 to change her back to normal by giving her a gift: leftover fries. When she's brought back to normal, she apologizes, to which Santa forgives her, though she scolds him for trying to swipe a fry, telling him to get his own.
The show's portrayal of Santa is different than most versions. He's not as fat or jolly, and far more heroic. He also shows above-average strength, ripping off the door of the room where the Delightful Children were.