Our Ancestors the Humans is the 44th episode from Season 1 that aired on August 7, 2000.
Etno has constructed a time machine, but also has a huge debt. The aliens set the time machine to different eras, but there is no escape from the tax collector.
Etno has constructed his world's first time machine, but it also has a huge debt, owing the aliens 23 years of back-taxes. Plus, if they don't pay up or fork over the money, the tax collectors, Nefu Ganioni and his assistant, Alex will confiscate the furniture and everything on the Aliens' house.
So, they set the time machine to three different eras, including the prehistoric Stone Age, fantasy themed Medieval Ages and the future, but there is no escape from them. At the end, Nefu rings the doorbell and the Aliens are seeing the three different era versions of both of them, plus they've fainted.
- The quote which Nefu Ganioni is saying, "You owe twenty-three years of back taxes," was similar and used by Candy, saying "It demands 23 light years in back taxes.", on his letter from the IRS being delivered by the blue mail-alien from the episode, Bad Luck Blues.