Calamitous is tiny, near-sighted, eccentric, old genius, who is one of the most brilliant evil minds on the planet, and he would be more dangerous if he didn't have the bad habit of never finishing what he starts. Calamitous is determined to get Jimmy to finish his projects for him because he cannot finish them himself.
Once, Calamitous was an intelligent child who never finished anything, from food to sentences. His inability to finish things lead him to never finishing his homework as noted by Ms. Fowl which strengthens the idea he was held back. Later he overcomes this and is heard completing sentences after he took a self-help class. Calamitous seems to like Ms. Fowl. He often wears a lab coat, long black gloves, and eyeglasses. Calamitous has gray hair. Calamitous has a robot called the CalamiBot, which he has used as a bodyguard and as a disguise.
He is also the final boss in "Nicktoons Unite!" and "Nicktoons: Attack of the Toybots," where he faced (besides Jimmy and Timmy) Danny, SpongeBob and other heroes, and he appeared in 2006 PC Video Game Called Nicktoons Winners Cup Racing as an Unlocked Playable Character by winning the Grand Prix mode, you'll be able to unlock multiple villains to against, such as Plankton, Mr. Crocker, and Vlad Plasmius, or you could open other tracks to drive on, such as challenge levels. In a race, Powerups can be acquired other racers. Some of the courses are based directly on the characters in the game. Mini-games is available, but players have to unlock them before they can play them.
- Even after taking the self-help class, there are still times where Calamitous may not finish things as he admits to not finishing the class. Since he also stated that he meant to finish, it is possible that after "Operation: Rescue Jet Fusion," he did make up for the session he missed and has now completely overcome it.
- Despite being the main antagonist of the TV series, Calamitous doesn't appear much.
- Calamitous may be in his 50s, 60s, or early 70s.
Main Characters: Jimmy Neutron | Carl Wheezer | Goddard | Sheen Estevez | Cindy Vortex | Libby Folfax | Nick Dean | Goddard | Hugh Neutron | Judy Neutron