Carl Wheezer

Carlton Ulysses "Carl" Wheezer is Jimmy's neurotic, llama-loving, best friend. According to canon, he is 11 years old. Carl is known as nervous, timid and suffering from hypochondria. At times, he tries to overcome these personality traits in order to appear "cooler" around Jimmy and mutual friend, Sheen, even though he has a sensitive scapula. He has many talents, the most recognizable is his phenomenal singing.

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. Though, in "Carl Wheezer, Boy Genius", his love interest was Elke Elkberg, his Swedish pen pal.