Appearances in Christmas specials
The Adventures of Jimmy Neutron, Boy Genius
In the series' Christmas episode "Holly Jolly Jimmy", it is revealed that Jimmy is the only kid in Miss Fowl's class who refuses to believe in Santa Claus, much to the dismay of his friend Carl. Jimmy explains that the reason for this is that, two years prior, he asked Santa to bring him a core sample from Dwarf Star NG-7-38, but did not receive it. To prove his point, Jimmy brings Carl and Sheen with him to the North Pole. When they actually do find Santa's workshop, Jimmy is still unconvinced that Santa exists, thinking the workshop is just a regular toy factory. When Jimmy's DNA tracker overloads and shoots out a beam that scrambles Santa's atoms, Jimmy declares that he will deliver all of Santa's presents himself, saying that this will prove there is no Santa Claus. Jimmy seemingly manages to pull this off, but he forgets to bring all the presents that are supposed to go to his hometown of Retroville, and in his attempt to get back there, his rocket ship ends up crumbling, sending him and his best friends falling from the sky. Fortunately, Santa, now back to normal, rescues them and brings them back to their homes, along with their respective presents. To Jimmy's delight, he finds that Santa has given him the dwarf star core sample he wanted two years ago; it just needed 5 years to cool off.
Other Christmas productions
Prior to his own show's Christmas special being produced, Jimmy was featured in the Merry Nickmas interstitial shorts that ran on Nickelodeon in 2002. His most prominent role in these shorts was in "Patrick the Snowman", in which he, Cindy, Carl, Sheen, and Libby build a snowman that looks like Patrick Star, and Jimmy uses his Spoofinator 4000 to bring it to life. After the kids quickly grow annoyed with Patrick's antics, Jimmy decides to send him 70 years in the future, which results in Patrick annoying them again in that time. Jimmy also appeared as one of the elves in "Holiday Party", telling his chief, Zim, that his fellow elf SpongeBob SquarePants actually wants to be a fry cook. And in "The 12 Days of Nickmas", Jimmy sings the line, "Eleven clones attacking!", after which he is chased offscreen by Carl and his clones.