Jack is a one-off Brantford resident and common criminal, appearing only but prominently in "The Intruder". He is a professional burglar who breaks entry into the Parrish Mansion to steal any valuable belongings, while Nora Shepherd was out. Judy and Peter try to flee him by going to Jumanji, only for him to be sucked in, as well.
AppearanceJack is a young man in his mid or late 20s, wearing jeans, a black robber's leather jacket and matching beanie hat. Unusually, he loses his hat in Jumanji and never gets it back, and he gets holes in his jacket and pants during his stay.
Jack is a very sneaky, cunning and untrustworthy young man, as he frequently fools Peter, Judy and Alan at different points to his own advantage, going so far as to pretend to fall in one of Van Pelt's traps to lure Peter out, often ties the kids up and even throws Alan into a pool of Giant Snapping Turtles and rapids. He is also very ungrateful, as he was victim to hostile animals and plants in Jumanji, only to be saved by the trio but quickly double crosses them again.
Nevertheless, Jack is very charming as he notices Peter finds him somewhat cool and exploits it to his advantage, trying to get Peter's confidence by claiming that as "guys" they have more in common than Peter has with his sister, referring to it as a bond they now share. However, when Peter realizes that he is beyond redemption, he attempts to lure him into Van Pelt's Lodge by claiming that there is a chest full of emeralds in there. Jack sees through it and tells Peter to retrieve them for him, leaving him to do the dangerous work.
Jack also displays cowardly traits as he is traumatised by his experience in Jumanji, due to being attacked by animals, plants and when he finally escapes from Jumanji, he begs Bentley to arrest him.
After Peter is fascinated by watching an R-rated film, he and Judy head upstairs to play Jumanji and encounter Jack, who broke in through the window and prevents them from fleeing. They roll the dice to try to escape him, but the game brings him into their turn as well. Judy escapes by lying she needs to go to the bathroom and heads to Alan's for help.
When they approach Van Pelt's Lodge, Peter pretends to gain Jack's favour by lying that Van Pelt is a billionaire with valuable treasures, giving Jack an incentive to send him up to find something to suffice. When Alan and Judy show up to save Peter, Jack throws Alan into a pool of Giant Snapping Turtles and rapids, lying that he tried to save him, and ties up Judy in order to force Peter to bring him the alleged emeralds from Van Pelt's lodge.
Alan survived his brush with death and helps Judy and Peter escape Jack, only to find out the chest of emeralds actually contained a legendary Juroceros horn instead, attracting one which violently attacked Van Pelt in the middle of his gloating. The trio later find Jack, struggling to survive on his own and they decide to help him return to Brantford with them, only for Jack to run off with the chest and leave them behind.
Jack soon got his due comeuppance when the Juroceros pursued him for holding onto the chest, being forced into a corner and discovering to his dismay that the chest had no emeralds at all, solving the clue that the Juroceros hunted the hunter (Van Pelt) and Jack was therefore robbed of his emeralds.
Back in the Parrish Mansion, Judy and Peter run for the from door, meeting Officer Bentley in the midst of his investigation to find a reported prowler in Brantford. So traumatised by his ordeal in Jumanji, Jack begs Bentley to arrest him, which Bentley obliges.
- Jack may not be his real name at all.