Sgt. Frog Episode 76: To the Moon, Palace!
Episode 76 of 358 of Sgt. Frog, aired September 16, 2005, 25 minutes. Available with English subtitles and dub where released.
Episode summary
After selling resort homes on the moon, the Keroro Platoon decides to get around to actually building them. Natsumi and Fuyuki volunteer to go with them on a moon vacation, too! Source: crunchyroll