Jonas Venture, Jr.
The Venture Bros. character
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Jonas Venture, Jr. on Spider-Skull Island
First appearance

Return to Spider-Skull Island
Last appearance

All This and Gargantua-2
Voiced by

James Urbaniak
Aliases J.J.

Founder and former CEO of Ventech Industries

Curator of The Jonas Venture Jr. Museum of Jonas Venture
Relatives Lloyd Venture (great grandfather, deceased)
Jonas' father (grandfather)
Jonas Venture Sr. (father; deceased)
Thaddeus Venture (twin brother)
Hank Venture (nephew)
Dean Venture (nephew)
Dermott Fictel (nephew)
The Monarch (blood relative)
Sally Impossible (girlfriend)

Team Venture
Sally Impossible (romantic)

Dr. Jonas Venture, Jr. (sometimes called J.J.) was the son of the late Jonas Venture Sr., younger twin brother of Dr. Thaddeus "Rusty" Venture and uncle of Hank Venture, Dean Venture and Dermott Fictel, and the founder and CEO of Venture Techno Industries. He was one of the supporting characters on the Adult Swim show The Venture Bros. He is voiced by James Urbaniak. Urbaniak has stated that first-season J.J. is vocally patterned after Charlton Heston. He is presumed dead after Gargantua-2 exploded.


Dr. Venture's dream where he is attacking Jonas Jr. in the womb; these Dreams were intended to give the False Impression that the situation was the other way around, with Thaddeus himself being attacked.


Although Jonas Junior is the fraternal twin brother of Doctor Thaddeus Venture, his existence was unknown to the rest of the world for forty-three years. Somehow, Thaddeus "absorbed" his brother in the womb without killing him, possibly a case of "Fetus-in-fetu". (He may have retained some sort of primal memory of the act, as for most of the first season Thaddeus was haunted by recurring nightmares of a fetus swallowing, strangling, or otherwise harming another near-identical fetus.) Against all odds, Jonas Junior not only survived inside Thaddeus' torso for over four decades, but remained conscious enough to be aware of his brother's thoughts and activities.


Jonas Jr's original robot body.

When he judged the time to be right, he caused Thaddeus great pain from within until doctors removed his underformed body, assuming it was a tumor. Free at last from his organic prison, Jonas quickly returned to the Venture Compound in secret and constructed an enormous robotic body for himself. He easily neutralized Brock and nearly succeeded in killing Thaddeus, but was foiled with the assistance of H.E.L.P.eR.. In a rare moment of compassion, Thaddeus prevented Brock from killing his brother and offered him half of the Venture "empire" in reparation for trapping him for decades. He also allowed his brother to name himself Jonas Venture Jr..As the brothers made their peace with each other, Jonas agreed to take, among other assets, the X-2 (Venture Industries' research ship) and the Venture Compound on Spider-Skull Island.

As a Super Scientist

Jonas' body was unable to fully develop while inside his brother; standing roughly two feet tall, his appearance is similar to that of a dwarf while his left arm is largely vestigial. After reconciling with Thaddeus, Master Billy Quizboy and Pete White fitted him with a bionic arm similar to Billy's. Within the space of a few months (in the hiatus between the show's first and second seasons), Jonas grew his hair out to a ponytail, earned two doctorates, lost some of the weight he had accumulated from living inside Thaddeus' body with little activity, developed a slightly less hoarse voice, and generally began repairing some of the damage that Thaddeus had inflicted through incompetence upon Venture Industries. Proving himself more capable than his twin, Jonas completed the majority of Thaddeus' contract work with the government by the time his brother returned. He also built the X-X-1, an improved version of his father's X-1 jet plane with a list of additional amenities including a fully automated autopilot mechanism, and a lounge with Space Invaders. He eventually built Venture Techno Industries (Ventech for short) and released a series of new highly popular products such as the J phone. He purchased a skyscraper in New York city naming it Ventech tower where he kept his primary residence.

Recently in season four, it is revealed that Jonas Junior is in space in orbit of earth and currently building another Gargantua space station. Sally is shown helping him in the process with other allies and subordinates, such as Hector and Swifty.


In All This and Gargantua-2, J.J reveals to his brother that he has cancer and is slowly dying. When Gargantua-2 suffers a meltdown, JJ later sacrifices himself (along with General Treister) in order to save the guests on board the space station. Whether he is truly dead is debatable as Venture Bros is known for ironic twists. His testament dictated that Ventech industries and it's subsidiaries are to be given to Rusty upon his death.

Contrast with Thaddeus Venture

Jonas Junior seems to be nearly everything that Thaddeus is not: competent, productive, physically fit (despite his dwarfism), self-confident, modest, kind, accepting, suave, and successful with the opposite sex. He is pretty much identical in performance and general appearance to his father, Jonas Venture Sr.. Jonas Junior once said that he is the son that should have carried on the Venture legacy, rather than Thaddeus. Despite his diminutive stature and mechanical arm, he has proven very attractive to women, the latest of which is Sally Impossible (who has moved in with Jonas, and seems to have established a happy family life with).

After reconciling with his brother, his personality seemingly transformed from that of a fratricidal maniac to that of a jovial genius, while Thaddeus has remained a bitter, cynical, socially awkward recluse. In the episode Now Museum-Now You Don't, which deals with Jonas establishing a museum on Spider-Skull Island to honor his father's memory, Jonas' personality is shown to be more manipulative, paternally condescending, domineering and brittle than in past episodes, with a desire to minimize Thaddeus' past role in Team Venture. Whether this is a true indication of his character is up for debate, as Brainulo was present and emphasizing hostilities/unpleasant traits of everyone at the museum's opening; additionally, these negative traits of Jonas Jr.'s could simply have been the stress of arranging a large party, full of his father's peers, with minimal assistance and no support/input whatsoever from Thaddeus.

Although "J.J.", as he calls himself, is much less oblivious than Thaddeus, he is not completely unflappable. While on a mission to retrieve the hidden components of a mysterious device his father built, he was confronted by a drug-crazed, bedraggled Jonny Quest. J.J. was at a loss until his colleague (an ex-"ghost pirate" captain) soothed the paranoid, ranting man with the prospect of falsified prescriptions (in a deleted scene for the episode, Venture expresses his disdain and remorse for this action, on ethical grounds). Jonas and the captain were later captured by Richard Impossible under unexplained circumstances. Jonas helped save the day, however, by communicating with H.E.L.P.eR. via a collar-mounted communications device ("What kind of an idiot would strap his only means of emergency communication to his wrist? They always tie you up!"). After assisting Brock in defeating Impossible, J.J. began flirting with Richard's emotionally-starved wife Sally, true to his ladies'-man personality. Eventually, Sally, Ned, and her son are seen living at Spider-Skull Island with him, he and Sally sharing a loving relationship and Ned happily hugging Jonas (hard enough to occasionally cause a 'brain vein').

There is also the possibility that Jonas Junior's apparent competence and good-natured personality are an ironic twist of fate, particularly given his claim in his first appearance the he was the son that Jonas Venture Senior should have had. Given the increasing indications in Season 3 that many of Thaddeus' issues and failings are the results of shortcomings in his father's parenting, combined with various traumatic experiences incurred during his childhood as a boy adventurer, it could be surmised that Jonas Venture Junior is able to fulfill the role expected of a son of the great Dr. Venture better than his brother, due to the ironic fact that unlike Thaddeus, Jonas Junior wasn't actually raised by their father.



Jonas Venture Sr. (Father)

Is the father of Thaddeus and Jonas Jr., whom he never met due to being eaten and trapped inside of brother for over forty years. Despite never knowing his father, JJ is shown to deeply respect him even once stating to Thaddeus that he was suppose to be the true son of their late father. JJ's idolization of his father is so great that he would even name himself after his father and later going off to create a museum on Spider Skull Island where he and guests would commemorate the legacy of his father.

Unknowingly, JJ was responsible for finding and bringing his father's head (which was in a machine) back to VenTech Tower. JJ died without knowing that his father was still alive while Jonas Sr. didn't know of their connection and mostly referred to him as a "savior".

Thaddeus "Rusty" Venture (Older Twin Brother)

Is Jonas Jr.'s older twin brother who had devoured him while they were still in the womb over forty years ago. When Jonas Jr. was liberated from the inside of his brother, he immediately tried to kill his brother for devouring him while they were in the womb forty years ago. Thaddeus was shocked at the revelation of having a brother as his recently revealed twin showed nothing but contempt and vengeance against his brother even declaring to Thaddeus "You stole my life from me! Well guess what Rusty I'm taking yours claiming my birthright. The Venture empire is mine !!!". However, when J.J. was defeated and was about to be killed by Brock, Thaddeus (in a rare moment of compassion) stopped him calling the dwarf his "brother" and in an attempt to make amends for trapping him for over four decades gave him half of Venture Industries.

Thaddeus' attitude towards Jonas has changed radically, perhaps because he senses that in a short period of time, Jonas Junior has made great progress towards fulfilling the world's expectations for the son of Jonas Venture Senior (which Thaddeus had utterly failed to do in his entire adult life). By the beginning of the second season, Thaddeus had begun treating Jonas with the same contempt he displays for nearly everyone else, avoiding him whenever possible and bitterly mocking him when forced to interact with him. Jonas Junior, however, appears to ignore his brother's scorn in a good-natured manner.

While jealousy and bitterness do drive a wedge between the brothers, it appears that they do not completely despise one another; in The Doctor is Sin, Thaddeus was given the opportunity to become a supervillain and the arch-enemy of Jonas Jr. as a way of dealing with his sense of inadequacy instilled by his father. Thaddeus declined without stating a given reason, additionally giving up the numerous benefits arranged for him by his benefactor, Dr. Henry Killinger; the incident left him feeling drained and intensely depressed, while also debating as to whether he was an immoral person or not.

At the start of Season 6, JJ started to treat his brother with respect and told him how he got all the good genes and had people that he can rely on. He then confessed that he had cancer and was dying, which completely shocked Thaddeus who hugged and held his brother in his arms for a while. In his final moments, JJ happily bid his brother farewell before sacrificing himself (along with General Treister). During his funeral, he gave his brother the multibillion dollar HQ of Venture industries in New York something that caused Thaddeus to faint. In Hostile Makeover, when hearing a recording of JJ's voice on Dean's phone, Thaddeus went into complete silence and told Dean "too soon" showing he respected his brother.

Hank and Dean (Nephews)

While Jonas' nephews Hank and Dean seem to be mostly noncommittal towards their newly-discovered uncle so far, they retain a somewhat childish mixture of fascination and revulsion towards him due to his unconventional appearance. There have been slight hints that they share a much warmer relationship with him than Thaddeus does with either of them. Jonas had trusted them with the X-X-1 to find a missing piece of their father's device (a task they completed successfully), and he seemed happy to see Dean when attempting to break his brother's force-field while calling Dean "Nephew". At Jonas Jr.'s funeral, Dean expressed sadness at his uncle's passing and seemed hopeful when he thought Dr. Orpheus intended to resurrect him but was dejected when it turned out to be an old stuffed animal.

The Monarch (Self-made Enemy)

In Tears of a Sea Cow it was revealed that The Monarch was assigned by the Guild of Calamitous Intent as his new arch nemesis, though currently only on a trial basis. The Monarch proceeds to use Jonas in a plan to exploit a loophole in the Guild's rules that allows the Monarch to go after Thaddeus and his boys once again.

Since Thaddeus and The Monarch were said to be blood relatives, the connection applies to JJ and The Monarch as well.


Sally Impossible

In Twenty Years to Midnight, JJ expressed an interest in Sally Impossible and shortly afterwards the two began a relationship with JJ allowing Sally, her infant son and cousin Ned to move in with him on Spider-Skull Island. Not much is known about their except that it appeared to be strained as JJ was caught up in the extravagant life of a super scientist and carrying his father's legacy. It is unknown whether or not Sally knew that JJ was dying of cancer. She was distraught when JJ sacrificed himself to save all those on board Gargantua-2. At his funeral, his lawyer reveals that JJ has left Sally with a generous inheritance as well as the rights to Spider Skull Island showing that he truly cared for Sally. In Rapacity in Blue, Jonas shows how much he cared about Sally in a hologram alarm of him, by having it remind him to hug and tell Sally how special she is.


Team Venture

Perhaps due to Thaddeus' resentment towards him, Jonas Junior has had limited involvement with Team Venture since his emergence. This is ironic, given that he possesses what is probably the most competent scientific (and certainly the most well-balanced) mind on the show.

The original Team Venture holds him in similar contempt and interactions between them have been tense at best. However, they did seem touched after watching a film of Jonas Venture Sr., as well listening to JJ when he stated his reason for the museum was to honor the memory of his late father.

Episode Appearances

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