Dr. Jonas Venture, Jr., also known as J.J. (voiced by James Urbaniak): Dr. Venture’s deformed twin, who was absorbed by Rusty in the womb. Until the first season finale, he appeared only in Dr. Venture’s nightmares. He was freed from Rusty’s body via surgery after being mistaken for a tumor. Desperate to claim the life that was stolen from him, he tried to murder Dr. Venture using a giant mechanical suit that he made out of household items. Though he has the body of an infant, his head has matured to an adult appearance and bears a striking resemblance to that of his father. He also seems to have inherited his father’s brilliance, unlike Thaddeus, as he earned two doctorates within the period of a month (the amount of time Thaddeus had spent escaping his former life). By the end of the first season, Thaddeus has agreed to share his Venture birthright with his brother. He is given the old Venture compound on Spider-Skull Island, as well as the X-2, the boat built by their father. Jonas Jr. appears to be everything his brother is not: scientifically astute, hard-working, attractive to women, about two feet tall, and the possessor of a full head of hair.
Pete White (voiced by Christopher McCulloch): An albino computer scientist and co-founder of Conjectural Technologies. He went to college with Venture and Ünderbheit where he hosted a New Wave radio show called “The White Room”. After college, White and Billy Quizboy worked in tandem on a Jeopardy-styled gameshow, called “QuizBoys” in which Pete hosted and Billy participated. After a debacle concerning the show seeding Billy’s answer display with the correct answer, regardless of what he put down, White and Quizboy were fired and left to find new lives. While the two had a short falling out, Pete eventually rejoined Billy (after his short unwanted stint with O.S.I. and his task of spying on Phantom Limb). They find refuge in a trailer near the Venture Compound where they currently reside. Like Venture and Quizboy, White tends to be somewhat lazy and half-hearted in his efforts. On occasion, characters refers to him as “the gay albino”, although it is unlikely that he is truly a homosexual.
Master Billy Quizboy (voiced by Doc Hammer): A self-proclaimed “boy genius,” Billy Whalen is actually an adult (35 in “The Buddy System”, 37 in “Handsome Ransom”) with a speech impediment and growth hormone deficiency. He suffers from hydrocephalus, although his intellect seems to be unaffected by this condition. He starred as a contestant on the game show Quizboys hosted by Pete White. When White gave him the answer to the final question, they were both kicked off the show and Billy’s winnings were frozen by the FCC. White and Billy went to Mexico, where Billy was accidentally entered into a dog fight, thinking it was an underground quiz match. Billy lost a hand and eye in the mix up. Billy left White, and was recruited by O.S.I. agents Brock Samson and Hunter Gathers, who provided him with a mechanical hand and camera eye. Brock and Hunter sent Billy undercover to spy on Professor Fantomas. Fantomas had Billy help with his experiment, but the experiment went wrong, Fantomas became Phantom Limb and Billy lost his left eye again. After a mind wipe, Brock (newly assigned to Venture) smuggled Billy out of O.S.I. and left him with White. He then became a neurogeneticist and co-founder of Conjectural Technologies. He is a virgin as revealed during a conversation with Pete White and Dr. Venture. In “The Invisible Hand of Fate”, Billy hits his head on a toilet and remembers everything.
The Pirate Captain (real name unknown) (voiced by Christopher McCulloch): The leader of the “ghost pirates” in the episode “Ghosts of the Sargasso”. After his initial encounter with the Venture family, he began living on the X-2 after having difficulties in finding a job. When Jonas Jr. acquired the ship, he hired the captain. He has not been referred to by any name or nickname other than “The Captain” so far. He currently resides with Jonas Jr. on Spider Skull Island and fulfills the duties of a butler, caretaker, and right-hand man. The Captain always refers to Jonas as “Chairman”.
Triana Orpheus (voiced by Lisa Hammer): Dr. Orpheus’s 17-year-old quasi-goth daughter. She has purple hair, and is fairly friendly with the Venture Boys. She is possibly the most down-to-earth character on the show, despite her father’s tendency to dramatize. She takes an interest in kitsch.