In the year 1999, planet Earth found itself under attack by aliens... or it did in the dreams of paranormal enthusiast Fuyuki Hinata, at least. But when his fierce-tempered older sister Natsumi jokingly pointed at the wall and said 'Look! It's a real, live alien!' little did she know that Sgt. Keroro of Planet Keron's invasion force had selected that exact spot as a hiding place! With his cover now blown, the Sgt. is forced into doing chores for the Hinata household, while he attempts to re-establish communications with the rest of his platoon and devise plans for world domination!
It is the Edo period, an era when samurai are still of great importance - at least they used to be, until all sorts of aliens called the Amanto decided to take over the government and revolutionize Japan so it wouldn't be so uncivilized. In Edo, now a city where anachronism is the rule rather than the exception, Gintoki, a former samurai, tries to make a living doing odd jobs. During the course of his work, Shinpachi, a would-be samurai; and Kagura, an absurdly strong girl, join him. Of course, he has them work for free, how else would Gintoki be able to buy Shonen Jump and strawberry milk, let alone pay for unimportant things like rent if he has to support someone other than himself?
These two are just as random as the latter and the content will range from mild to extreme. While Gintama is significantly more violent than Keroro, Keroro is much more heavy on fan-service, nudity and sex jokes. Both are gag series and pokes fun at pop-culture, Anime, Manga and everything else.