Professor J.S. Heinrich Ibsen

The mad scientist of Jumanji. He invents dangerous Steampunk-like machines. Ibsen is tasked to "work" for Jumanji, creating dangers and nightmare machines like poisoned acid-spitting frogs and battle-armored rhinos. He sends daily reports to "Jumanji" itself which broadcasts throughout the jungle. He calls himself a "Master Builder of Jumanji." This is a reference to the Norwegian playwright Henrik Ibsen and his play "The Master Builder".

Episode of Jumanji
Master Builder (October 13, 1996) – During another visit to Jumanji with the clue "I can make fish swim, I can make birds fly, I can make you run just don't ask why," Peter reveals he stole Judy's laptop computer and brought it with him to Jumanji to solve Alan's clue. Judy instead has Alan describe everything he learned in Jumanji over 20 years, to configure a solution. Sunset approaches and they must escape the cave as "Verbilangs" come out and attack at night. Professor Ibsen gives them a lift to his laboratory, where Alan sees all the dangers he's faced in Jumanji. Ibsen reveals he creates the dangers in Jumanji. He sends a daily report to "Jumanji" itself, which broadcasts throughout the jungle. Judy plugs a large mainframe computer into her laptop which gives her laptop the ability to analyze everything in Jumanji and predict the future, revealing that within seconds a flash flood will hit. The trio escapes to high ground, and are chased up a tree by mechanical hyenas. Judy tries to get finds Alan's clue, just as Ibsen knocks the tree down to steal the laptop. He uses it to create even more monstrous creatures, reform damaged ones, and reshape the terrain to make it more dangerous. The trio race through the jungle while he is busy doing his daily report. During the report he makes a speech about how he now rules Jumanji and Peter figures out their clue. At his lab they try stealing the computer back, but his machines attack, and then the computer overloads creating a cyclone. Peter realizes their clue ties in to how to stop the computer. He asks it "why", which it tries to answer but cannot since it has tno context and it shuts down. Ibsen shuts down too, revealing that Ibsen is also a machine. His factory is destroyed and the kids return home. At home Judy tells Peter to finish his homework before they return to Jumanji and offers him the use of her computer which she'd denied him earlier, but he decides to do it by hand.

Gift (February 16, 1997) – Judy and Peter enter Jumanji for Alan's birthday with the clue "Release the thing you most adore, it comes back closer than before." During the trio's picnic, Peter annoys Judy when he gives Alan Judy's Swiss Army Knife as a gift. They are attacked by a swarm of giant Jumanji ants, then by a giant centipede when they flee into a cave. They escape the centipede by going upriver in a raft, but Alan was bitten by the centipede. The green venom flows through his veins toward to his heart. if it does, he'll die. Alan collapses when they reach shore, and the children bring him to shelter. Peter vows in anger that he'll destroy the game if Alan dies. Without noticing, The Vengeful Grim Reaper, Stalker overhears with the microphone, disguised as a flower plant. Stalker vows to kill the children and Alan in order to protect Jumanji, enlisting Slick, Van Pelt, and Ibsen to do the task. Alan dips into a magic pool that allows him to rest and shows his dreams in the water. Peter tricks Jumanji into letting him return to the real world (by pretending his cap is the thing he most adores), where he tries to find a cure for the bite. He fails as the game realizes his lie and sucks him back in, transforming him into a frog. Judy ventures to Slick's looking for a cure. Instead, he gives her "Jumanji Tracking Juice" in exchange for her shoes which reveals her footprints and allows the evil trio to hunt her. The three apes deplete the juice before the villains find her. Peter journeys to the Manjis to meet Tribal Bob, who is being watched by the villains. He does plant a small statue on Peter's head without Peter noticing, who is then stalked by the villains. He manages to elude them, and Judy finds the statue, of a mosquito. They realize a Jumanji mosquito can suck out the venom from Alan's veins. But upon capturing one, the villains attack, armed with weaponized vehicles from Ibsen. The kids elude them, and Tribal Bob and the Manjis carry off the villains. Judy and Peter arrive to cure Alan, but are confronted by Stalker himself. As Peter fends him off, Judy tries to cure Alan, when in the pool she sees Alan is dreaming about when he entered Jumanji. She needs only a few seconds to see the clue, but Alan is closer to death than that. She relents when the venom reaches Alan's heart and has the mosquito suck out the venom. The mosquito then crashes through the image, destroying it just before they can get the clue. Fully healed, Alan then shoves Stalker off a cliff and down to the bottom of the waterfall, saving Peter. Judy gives Alan her knife as a gift having learned from his dreams that he considers them his family and it solves the clue and Peter returns to normal. Alan promises that they'll finish his party when they return as they leave. After Judy and Peter leave, Stalker emerges from the water and vows for more revenge someday.