Episode 311
The Keroro Platoon has the horrifying realization that it's Kululu's turn to come up with an invasion. They have to stop him, at all costs! And then Keroro comes up with the idea to ply Fuyuki with feel-good stories until he is moved to return the Kero Ball to them. The stories don't quite have the effect they anticipated. Source: crunchyroll
Aired 24/04/2010EP 311 - Episode 311
Sgt. Frog
Keroro is a frog-like alien sent from his home planet on a mission to conquer Earth. But when his cover is blown, his battalion abandons him and he ends up in the home of the Hinata family. There, he's forced to do household chores and sleep in a dark basement that was once supposedly a prison cell haunted by the ghost of an innocent girl. He even spends his free time assembling Gundam model kits. During his stay, Keroro meets up with subordinates who were also stranded during their failed invasion.
(Source: Anime News Network)