Swapper

Swapper is the second season premiere and the twenty-first episode overall.

Plot
When Teddy creates a body-switching device, it swaps William and Mark the Mailman's bodies.

Summary
Using signs, Teddy explains his newest invention: the body switcher. He explains that he hooked up the pressure plates that open and close William's front door, and Mark the Mailman steps on the other plate in an attempt to give William his mail. The two end up switching bodies, and William goes to Mark's house while Mark takes care of things at William's house. William notices that Mark doesn't have a roof over his house, which Mary announces she has been thinking about. William also finds Mike and Martha Mailman lying in twin beds. He then gets a call from Teddy and discovers that the machine has been fixed after Mark broke it, and goes over to the newly-rebuilt body switcher to swap Mark the Mailman and William into the right bodies again, breaking it a second time although they do not plan to fix it.

Trivia
This marks the first appearance of Mike and Martha Mailman, the twin children of Mark the Mailman and Mary.

In this episode, Mark's house is shown to be obsidian and roofless. However, in Garyzilla it appears to be a small wooden mobile home.