Jimmy, Carl, Sheen and Goddard travel to the moon to rescue Brobot's parents from a greedy alien known as the Junkman.
"The Junkman Cometh" provides examples of:
- Batman Can Breathe in Space: Lampshaded. Sheen asks Jimmy how they're able to breathe in space without wearing helmets, and Jimmy gives an explanation that is drowned out by Carl's singing.
- Captivity Harmonica: Sheen plays a harmonica while the boys are trapped in the Junkman's cell.
- Crying Wolf: Because Brobot lied about being in danger to get Jimmy to visit him on the moon, Jimmy doesn't believe him when he tries to warn him about the Junkman. Sheen even briefly tells the story of "The Boy Who Cried Wolf."
- Sequel Episode: To "Brobot".
- Shout-Out: The monolith from 2001: A Space Odyssey appears on the moon.
- The Unreveal: Jimmy's explanations for how they can travel to the moon in just minutes and be able to breathe in space are drowned out by Carl's singing.
