Sgt. Frog Episode 168: Keroro, The Big Plan for Period Restriction / Momoka, My Limited Tanabata
Episode 168 of 358 of Sgt. Frog, aired July 7, 2007, 25 minutes. Available with English subtitles and dub where released.
Episode summary
Keroro notices that when things are available as exclusive, limited-time-only versions, people value them more. So he has Kululu build a gun to turn anything they want into these! But when the exclusive items flip over to "no longer available," the trouble begins... Source: crunchyroll