Master Builder is the 5th episode of the Jumanji animated series. It marks the first appearance of Professor Ibsen, soon to be a recurring Jumanji inhabitant, as well as the notion that some of Jumanji's inhabitant wildlife are creations of his design.


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.