Gamakichi

is one of Gamabunta's children. He was first summoned by Naruto Uzumaki because Naruto couldn't focus his chakra during the beginning of the battle with Gaara. However, he is intelligent enough to be aware of the situation around him and realize when it's time to flee. During the Sannin battle, Gamakichi was accidentally summoned again by Jiraiya while he was fighting with Orochimaru because Tsunade had secretly fed Jiraiya a chakra-disrupting potion.

Personality
He is rather funny, and has the mannerisms of a smart allec. He is also often very condescending and joking in most situations, preferring the levity of talk to the seriousness of battle. He seems to favor Naruto because he saved him from Gaara's One-Tailed Shukaku form. When he is summoned he tends to greet people by saying: "Yo".

Konoha Invasion Arc
During the fight with the transformed Gaara, Naruto was slowly being pinned down, and decided it was time to summon Gamabunta. However, due to poor chakra control, he could only muster enough chakra to summon Gamakichi.

Later while fighting the fully transformed One-Tailed Shukaku Gaara, Naruto summoned Gamabunta, and though at first Gamabunta refused to help, Gamakichi riled him up by saying that the One-Tailed Shukaku tried to kill him, but then Naruto saved him. He also starts to make puns that Sakura is Naruto's girlfriend, which doesn't seem to bother Naruto at all.

Rice Country Arc
Jiraiya summoned Gamakichi again when it came to infiltrating Orochimaru's hideout, wanting to check the entrance for traps. During this time he greeded Naruto friendly and shocked Sakura by being a talking toad.

Post Hunt for Uchiha Arc
A little while after Naruto returns from his failed mission, so does the Pa Toad to inform Tsunade about Jiraiya's death. He is followed by many other toads, amongst others Gamabunta who with Gamakichi comes to tell Naruto to go to the Hokage's office. It is then revealed that Gamakichi had grown big enough to fill out the space between his fathers eyes, something not even the fully grown Jiraiya could. When he greets Naruto, he almost tells him why they are there. Gamabunta tells his son to "shut his trap" and let him handle it.

Past Speculation
Before his appearance in Part II a poster included with an issue of Weekly Shonen Jump has depicted a post-timeskip Naruto riding upon a much larger Gamakichi. In the poster, Gamakichi is now about the size of Gama and wields a large kunai. He also has a pipe, like his father. It is possible that Gamakichi will grow to be as large as his father one day, as hinted in the data books.