Zero Gravity is the 3rd (55th) episode from Season 2 that aired on November 16, 2002.
To the delight of the aliens, Etno has found the means and a way to make the house take off, like a rocket. But he gets his calculations wrong and the rocket heavily lands on the real moon. At least on the moon, there are no humans to bother them except at that very moment, a human astronaut rings the doorbell.
This plot is coming up soon.
If you want to see this transcript of this episode, click on to this link.