Sgt. Frog Episode 162: Chibi Kero, That Time Joriri
Episode 162 of 358 of Sgt. Frog, aired May 26, 2007, 25 minutes. Available with English subtitles and dub where released.
Episode summary
After Kululu locks the rest of the platoon into their new secret base, Keroro and the rest reminisce about their childhood secret base, and a strange Keronian they knew named Joriri. Source: crunchyroll