Professor Calamitous starts out as a student of Jimmy Neutron's teacher Miss Fowl, who has failed him for being a bad boy in school. He is also described as the man who can never finish anything according to Miss Fowl and Jimmy.
In the Series
Professor Calamitous makes his appearance as Jimmy's most recurring enemy than any other villain Jimmy has ever faced.
He makes his debut in the episode "Professor Calamitous, I Presume" when he first appears in a robotic suit which was finished. Calamitous plans to trap Jimmy and make him his slave. He ensures his plan by kidnapping Jimmy's dog Goddard. Jimmy follows Calamitous to his lair and finds that his theory about Calamitous not able to finish anything was right. He then comes out of his suit and makes Jimmy use a laser, and the test succeeds by firing at his door thus having Jimmy escape. But he tries to chase him down. He ends up defeated by Jimmy by claiming that he needed his suit to have a bathroom. Calamitous claims to get revenge on Jimmy and then flies away.
Calamitous next appears as the main antagonist of the hour long episode "Operation: Rescue Jet Fusion". He first appears observing both Jet Fusion and Jimmy in his trap thus completing his sentences (also having taken a self preservation class only missing one day). He explains his plan to flood the world by melting the ice and snow on Mt. Everest. He then orders his daughter Beautiful Gorgeous to do away with both Jimmy and Jet, who reluctantly escape Calamitous' clutches just as his lair was about to blow. He and his daughter are defeated when they rumble down the mountain to the peaceful land of Shangri Lama and are arrested for their crimes.
He makes a brief appearance in the episode "The Great Egg Heist" as the hidden antagonist . For the majority of the episode, he is disguised as a Chinese princess, who needs a jade egg to stop her evil brother from using a demolition device to rule the world, while in reality Calamitous built it. He then reveals himself after Jimmy gives him the egg and traps Jimmy and friends in a force field cell while he prepares his device. He faces defeat not knowing that the fake egg (Carl switched the eggs) caused a meltdown and sent him into the sky.
Calamitous next appears in the episode "Lights, Camera, Danger" as the hidden main antagonist. He appears first disguised as fame Hollywood director Quentin Smithee. Calamitous comes up with the plan to make a fake movie in order to get rid of Jimmy and his friends for foiling his previous plans. He reveals himself to Jimmy who realizes that Smithee is a fake and in reality it was Calamitous. He then unleashes a robotic snake on Jimmy. Jimmy's dad saves the day this time by throwing donuts into the the snake's mouth thus defeating Calamitous and destroying the snake's circuits. Calamitous is defeated by Jimmy who throws him into a police cab, thus taking him to jail.
Calamitous makes his next appearance (in a cameo) in the episode "My Big Fat Spy Wedding" as the minor antagonist who (in a televised version of himself) walks Beautiful Gorgeous down the aisle and accepts that his daughter is to be married to his old enemy Jet Fusion.
Calamitous makes his first to last appearance as a supporting antagonist in the episode "The League of Villains" where he along with King Goobot, Beautiful Gorgeous, the Junkman, Grandma Taters, Baby Eddie, the Space Bandits and Eustace Strych planning their revenge on Jimmy for foiling their every evil plan. He is partnered with Eustace on the task to distract Jimmy's friends by having Eustace give Libby a CD to dance to. He next appears laughing with the other villains at Jimmy. Calamitous next is shown as a member of the Villains jury while Goobot presides during Jimmy's court session. He then gives Goobot a plan combining all the villains ideas on how to destroy Jimmy. Afterwards, he gets disgusted by Beautiful Gorgeous and Junkman's relationship by trying to break them up. He is then shown trying to escape a T-Rex with the other villains while facing defeat.
Calamitous makes his final appearance in the crossover episode "Jimmy Timmy 2: When Nerds Collide" as the main antagonist alongside Anti-Cosmo. He makes his appearance first in his robot suit while robbing the bank bragging about his idea to finding a partner in crime to defeat Jimmy once and for all. He faces Jimmy but is suddenly defeated by him via anti gravity disc. Calamitous then spots Timmy fighting Jimmy in the sky via rocket. He observes Cosmo and Wanda and plans to enlist creatures like them in his quest to defeating Jimmy. Calamitous then follows Jimmy and his friends through a portal to Dimmsdale (with Jimmy's Hyper-Cube). He then runs into Anti-Cosmo after experiencing some bad luck. Calamitous forms an alliance with Anti-Cosmo only to find himself thrown in a cell of the Fairy-World prison after freeing the Anti-Fairies. He then forms an alliance with Jorgen Von Strangle only to find themselves at the hands of Anti-Fairies who have taken over Dimmsdale. Calamitous finds the Hyper-cube containing the Anti-Fairies and tries to get it. But Jorgen attempts to apprehend the Anti-Fairies only to find himself and Calamitous fused together. Calamitous then takes his new form to Retroville and plans to blow up his universe with a huge bomb. He (in Jorgen's body) engages the combined forces of Jimmy, Timmy and their friends (Cosmo and Wanda included) in a showdown for the safety of the universe. Calamitous tries to make Jorgen obey him but faces his final defeat when Jimmy defuses them back into their own bodies. Jorgen then stops him by shrinking him and putting him into a bottle. He swears revenge on Jimmy, but Jimmy assures him that he won't threaten anyone ever again.
Calamitous, much like stereotypical evil geniuses, while incredibly smart and evil, can also be somewhat comedic and absent-minded. His problem of forgetting things is always used to the heroes' advantage, and while he did go through shock therapy to cure himself, his problem somehow came back during the events of Nicktoons Unite!, as his defeat was because he forgot to make the Doomsday Machine with solar panels instead of plugs, which were turned off by SpongeBob. While he does love his daughter, Beautiful Gorgeous, he is always trying to get her to be evil like him, instead of just letting her do it her way, which creates some conflict between the two.
Role in the series
Professor Calamitous becomes a Villain Leaguer during the events of Nicktoons Reunited, becoming a fresh new addition to their gallery of geniuses that provide the power of science to the team.