Carl also appears to be in love with Jimmy's mother, Judy Neutron, accidentally saying that she is beautiful around Jimmy and Sheen, carrying around a picture of Jimmy's parents with his head pasted over Jimmy's father's face. And many times in the episode "Love Potion 976/J" Carl really dislikes Jimmy's father, Hugh Neutron, whenever he is around. Though, in "Carl Wheezer, Boy Genius", his love interest was Elke Elkberg, his Swedish pen pal who was voiced by Grey DeLisle.
Carl likes to eat, and this causes him to be overweight. When his parents expanded their cable line-up, Carl found himself focusing on a channel devoted to llamas and a show about a superhero called Llama Boy the Super Hero. He has adored llamas ever since, going so far as to join a fan club, The Llama Love Society. He once turned into a llama. He is allergic to almost everything.
In the episode, "Normal Boy," it is revealed that Carl is the inventor of the "Hot Dog Holder Deluxe", also known as "The Versa-Bun (which is a normal hot dog bun, that he didn't really invent)." It is revealed in "The Incredible Shrinking Town" that he took ventriloquist lessons, and that he can virtually imitate and sound just like everyone. It is also a hinted that he has some sort of dislike for Sheen. Carl enjoys playing a video game called Llamapalooza.
It was stated by himself that he as always wanted to touch a Llama in the Jimmy Neutron: Boy Genius Film
- Carl will meet Jeffrey and his team in Jeffrey & Friends meet Jimmy Neutron: Boy Genius.
- Carl will join the Cyberchase Fighters in Michael Buzz and Delete meet Jimmy Neutron Boy Genius.