Episode 307
When Fuyuki and company go with Keroro to school at night to dig up a time capsule that accidentally contains a "super-secret item," a mysterious mist rolls in. As the gang is separated by the mist, they ruminate on what their lives will be like 20 years in the future, when the time capsule is officially slated to be opened. Source: crunchyroll
Aired 27/03/2010EP 307 - Episode 307
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)