Jack Aufbau is the son of Doctor Aufbau, Leopold's teacher in RCT3Crashes100's Angry German Kid Series. Jack is shown to be just as insane as Leopold, and is around the same age, so it is assumed he also goes to Leopold's school. He has a tendency to get very angry, much like Leopold. He is one of Leopold's enemies, after he was defeated in a round of Team Fortress 2, and Leopold bragged about his win over Jack.

Jack Aufbau would have made his debut in Episode #5, but his role was replaced by Ultraman Belial. He is set to appear in a later episode, although he may be scrapped altogether.

The remnants of the episode where Jack would have made his debut can be found in the video Scrapped Nonsense - Original AGK #5, although the episode is incomplete.


  • Jack speaks in gibberish that resembles German, while his father speaks in clear English. The reason for the differing languages has yet to be revealed.
  • Jack Aufbau was originally going to be the character who snuck the Blue Orb into Leopold's room, but, like his debut, this role was replaced by Ultraman Belial.
  • Despite talking in gibberish, in his sole appearance Jack was able to code his own computer program to spy on Leopold, called AUFBAU.BAT.
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