Keroro came to conquer Earth and ended up doing laundry instead. The joke never gets old because the show doesn't either, spinning 358 episodes out of a single perfect premise: an alien invader slowly becoming part of the family he was supposed to destroy. This is what happens when you let a comedy breathe long enough to actually mean something.

Sergeant Keroro, a frog-like alien from planet Keron, leads an advance squad sent to conquer Earth, which his people call Pekopon. His cover is blown, his battalion leaves him behind, and he ends up in the home of the Hinata family. After subduing young Fuyuki and his sister Natsumi, he learns headquarters has abandoned any plan to retrieve his unit. Stuck with the Hinatas, Keroro is made to do household chores and sleep in a dark basement said to be haunted, and he spends his free time building Gundam models. He meets up with other members of his platoon who were also stranded, and together they plot world domination every day, only to be foiled each time. Living alongside humans, they come to see them as friends and allies. The result is a long-running sci-fi comedy built on an alien conqueror who can never quite get his invasion off the ground.