Sgt. Frog Episode 78: Frogs of the Bermuda Triangle!
Episode 78 of 358 of Sgt. Frog, aired September 30, 2005, 25 minutes. Available with English subtitles and dub where released.
Episode summary
Framed for a crime he didn`t commit, Keroro gets embroiled in the treasure hunt of a lifetime. Thanks to Fuyuki`s expertise in detective work and knowledge of mysterious ancient Earth sites, those Vipers don`t stand a chance! ...Right? Source: crunchyroll