Gamakichi (ガマ吉; literally "Propitious Toad") is one of Gamabunta's kids. He's best known for getting pulled into fights he didn't ask for—most memorably when Naruto first summoned him during his battle with Gaara, mostly because Naruto couldn't get a grip on his chakra control yet. Despite the chaos, Gamakichi's smart enough to read the room and know when to bail.
He showed up again during the Sannin battle, this time accidentally summoned by Jiraiya while he was already tangled up with Orochimaru. Turns out Tsunade had secretly dosed Jiraiya with a chakra-disrupting potion beforehand, which explains why he lost control of his summoning.
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