Gamatama is a tadpole from Mount Myouboku.
Manga debut: Naruto Chapter #429
Anime debut: Naruto Shippuuden Episode #162
Gamatama never developed the combat skills needed to summon shinobi, so he ended up working as a name-registration clerk at Mount Myouboku instead. It's one of those roles that keeps the place running even if it's not exactly glamorous.
Content compiled by AnimeList.moe from publicly available sources.
