Sgt. Frog Episode 100: Keroro - Eh? Who... am I? Who... is Anyone?
Episode 100 of 358 of Sgt. Frog, aired March 10, 2006, 25 minutes. Available with English subtitles and dub where released.
Episode summary
Not only has the entire Keroro Platoon lost their memories, but so have Natsumi, Fuyuki, and Mois! Who could have caused this, and what started the base`s self-destruct sequence?! Source: crunchyroll