(voiced by William Sanderson) - 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".