He is rather funny, and has the mannerisms of a smart-alec. 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.
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 master 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.
Gamakichi and Gamabunta share a strong bond as father and son. When Gamakichi is in danger during the fight with the One-Tailed Shukaku, Gamabunta is swift to react.
Jiraiya summoned Gamakichi again when it came to infiltrating Orochimaru's hideout, wanting to check the entrance for traps. During this time he greeted Naruto friendly and shocked Sakura by being a talking toad.
While Naruto is off training with Jiraiya, Gamakichi spends his time training with his father. He also grows considerably over the two years that he and Naruto see each other. Sadly when they do meet again it is under somewhat tragic circumstances.
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.
Gamakichi is able to redeem himself when Naruto is to travel to Myobukuzan and needs to travel by reverse summoning, something that Gamakichi seems rather excited to do. He is shown again when Pa is to train Naruto where he seemingly translates everything Pa says into ridiculous, but to Naruto, understandable things. When Naruto questions how he is going to become one with nature, Gamakichi suggests that he dies. Pa tells Gamakichi to stop with his ridiculous translations and tells Naruto that he doesn't have to die. Later on, he explains that he meant die as a human and become a frog due to letting out too much Sage chakra.
He appears alongside Naruto and five other toads to help fight Pain. Like his father, Gamabunta, he watches as Naruto takes off to face Pein. When Naruto calls for him, Gamakichi wastes no time hopping over to him with Fukasaku and Shima along for the ride. When he is ordered to take Tsunade away, does so without complaint, waiting for them to finish their converstaion and leaving when ordered to. Gamakichi takes Tsunade to Sakura, knowing she needs medical attention.