Hinata Family, Haru Returns
Aki mentions on the phone that "haru" is coming, and Keroro immediately assumes that it must be a person, not "haru" as in the season of "spring." Then there's a huge snafu with the Keron Army inviting the friends of the Keroro Platoon to come visit Keron... with some ulterior motive. Source: crunchyroll
Aired 02/04/2011EP 357 - Hinata Family, Haru Returns
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)