The Judge is an anthropomorphic ape-like law keeper of "Jumanji", that presided over the trial of Alan when he was accused of stealing the Singing Orb from its resting place.
However, he is not a benevolent Judge as he condemns all without regard to innocence. He is also very greedy as shown when he takes an orb from the Fludgels and is sucked into it. In "The Ultimate Weapon," the Judge was present at Trader Slick's auction for the Trans-Vector of Jumanji. His only weapon is "Justice" which is a giant gorilla.
In The Trial, Judy and Peter encounter Alan carrying a glass orb which he saves from accidentally going over a cliff, but ends up going over himself. Luckily he lands in a net that's one of Van Pelt's traps, but the three apes steal the orb from him and capture him in the net before taking him away. They take him to the Judge himself, who charges him with the theft of the Singing Orb (the glass orb he had) which the Primate Society of "Jumanji" have been protecting since "Jumanji" was created. When Alan tries to defend himself, the Judge tells him that he'll be having a trial. When Peter and Judy try to intervene, the Judge tells them that they can defend Alan at his trial and to return the next morning before having Alan taken to a cell and taking the Singing Orb as evidence.
The first witness in the trial is Trader Slick who reveals to the Judge that Alan bargained with him for a map of the caverns where the Singing Orb has always been kept. The next witness, Professor Ibsen reveals he crash landed a prototype gyro ousted the cave of the singing Orb, and saw Alan enter the caves. The third witness, Van Pelt testifies that he was tracking Water Buffalo and witnessed Alan leaving with the Orb in his hands. Later that night, desperate and at Peter's suggestion, the two try to break Alan out of jail, but a failed and are captured themselves, but manage to pass it off as just talking to Alan and are released. The next day Judy questions Alan on the stand who claims he found the Singing Orb in the grass and was returning it when the cave started to collapse. Slick, Ibsen and Van Pelt merely saw him while he was returning it. Only Judy and Peter believe him and Alan is found guilty and as punishment, Peter is sentenced to 40 years on Desperation Island. Alan desperately tries to tell the Judge something, but he's just ignored.
On Desperation Island, the Judge attends Peter's induction, showing off his Cerberus Dogs which patrol the island and make escape impossible. Alan and Judy soon arrive at the island, but they're captured by the Judge, expressing surprise that some tried to break into Desperation Island, instead of breaking out. Held captive, Alan reveals the true story: Judy and Peter forgive Alan, but the Judge decides to execute them. However, just before Alan can be executed, Eep returns with a group of Fludgels who exchange a giant orb for their freedom as they owe Peter Eep's life. The Judge accepts and the three are freed and the judgment fit the crime (the act of kindness was Eep saving them) Judy and Peter's clue is solved and they return home. Meanwhile, the greedy Judge is sucked into the Fludgels orb which amuses them and Alan.
In The Ultimate Weapon, despite his past defeat, the Judge returned to attend his invite to Trader Slick's auction for the Trans-Vector. Arriving in "Jumanji", Judy and Peter look around and find Van Pelt, Squint, the Judge, Ibsen and more "Jumanji" villains attending a special auction after receiving an invitation from Slick. The Judge is very interested in the legendary ancient Trans-Vector of "Jumanji", making offers alongside Von Richtor and Van Pelt, as does a desperate Judy. By accident trying to get the Trans-Vector, Alan is revealed and a struggle for the Trans-Vector ensues, until Van Pelt gets it and casts Alan into the Nightmare World. He tries to do the same to Judy and Peter, but the Trans-Vector is stolen by Ibsen, allowing them to escape.
The Judge later shows up and steals the Trans-Vector, but when Ibsen traps him, he opens a portal to the Nightmare World that starts to suck up everything and Ibsen joins the kids in order to try to avoid being sucked in and the Judge escapes from the lab. During the chase, Squint tries to get the Trans-Vector and fails, but Peter and Judy manage to jump onto the back of the Judge's vehicle. He tries to cast them into the Nightmare World, but they're saved by Van Pelt and Von Richtor unintentionally capturing the Judge instead.
As The Judge and Squint try to pull them up, Peter and Judy untie themselves and quickly open a portal to the Nightmare World which they escape through. On the run, Peter manages to align the Trans-Vector and opens a portal back to "Jumanji" that they escape through. There they encounter Van Pelt, Von Richtor, the Judge and Squint, but Ibsen takes the Trans-Vector and plans to use it to send everyone to the Nightmare World before he destroys it, but Alan knocks it out of his hand with a rock, but it lands so that the portal is still opened and the villains run away and the creature chasing Alan in the Nightmare World comes through.