Gamakichi

is a toad from Mount Myōboku.

Personality
He is rather comedic, and has the mannerisms of a smart aleck. He is also often very condescending as well as light-hearted in most situations, preferring the levity of talk to the seriousness of battle. He has formed a bond with Naruto because he saved him from Gaara in his miniature Shukaku form. After he is summoned he tends to greet people by saying, "Yo" (in English dub, "Hey").

In Part II, Gamakichi has not just grown in size but in maturity as well. Gamakichi seems to have a considerably large amount of knowledge when it comes to human-toad combination techniques and natural energy. Also, he seems to be on better terms with his younger brother, Gamatatsu, as shown by him no longer calling him an idiot.

When summoned during the Fourth Shinobi World War, Gamakichi is shown to have started smoking like his father.

Appearance
Gamakichi début as a young orange toad with purple markings around his eyes, mouth and stomach. In Part I, he was small enough to fit on top of Naruto's head like Akamaru could fit on top of Kiba's head and wore a blue jacket. In Part II, during the Invasion of Pain, Gamakichi had grown big enough so that Naruto could stand on his head, but was still small enough that he stand on Gamabunta. By the time of the Fourth Shinobi World War Gamakichi has matured further, and is now nearly as large as his father with Naruto riding on top his head, just as the Fourth Hokage and Jiraiya once did with Gamabunta. Similarly to his father, Gamakichi now also smokes a cigarette and wields a giant sword. He also wears a necklace with a large bead.

Abilities
Though his abilities have not been expounded on much in the manga, in the anime, Gamakichi has shown a variety of techniques. He has been shown to be able to shrink his body size for infiltration purposes. He's shown the ability to use the Reverse Summoning Technique and summon Naruto to Mount Myōboku. During the Fourth Shinobi World War, Gamakichi is weilding a tantō, like his father with his abilities presumably improved a great deal as Naruto spoke very highly of Gamakichi when summoning him.

Nature Transformation
In the anime, Gamakichi has shown the ability to use Fire Release techniques, which includes the Fire Release: Flame Bullet and the collaboration technique with his brother and Naruto called the Wind Release: Toad Oil Flame Bullet.

Invasion of Konoha Arc
During the fight with the transformed Gaara, Sakura Haruno was slowly being crushed, and Naruto decided it was time to summon Gamabunta. However, due to poor chakra control, he could only muster enough chakra to summon Gamakichi. Despite being irritated, Naruto kept Gamakichi safe from Gaara's attacks. When Naruto finally managed to summon Gamabunta, Gamakichi convinced his father to help in the fight, telling his father that Naruto had saved him from Gaara and that he in turn, needed help saving his "girlfriend".

Search for Tsunade Arc
During the fight against Orochimaru, Gamakichi was inadvertently summoned by Jiraiya due to the crippling effects of Tsunade's drug which were still in his system, rendering him unable to properly control his chakra. He would later tell his brother Gamatatsu, who was summoned by Naruto, to run away when their father, Katsuyu, and Manda with their respective summoners were about to fight. Gamakichi later watched from the sidelines along with Tonton and his brother as the battle between the three waged on.

Land of the Rice Fields Arc
In the anime, Jiraiya summoned him once again to check for traps at the entrance of Orochimaru's hideout.

Land of the Birds Arc
Gamakichi made a short appearance in the Land of Birds when he and Naruto needed Gamatatsu. Despite Naruto thinking he would be useless, Gamatatsu, using his curiosity, found a kite that was a clue to how the Cursed Warrior flew. Later, he went down a dark tunnel with Naruto and Gamatatsu, and was caught by the daimyō and his guards.

Land of the Sea Arc
He was summoned again with Gamatatsu by Naruto in the Land of the Sea, although it was another attempt by Naruto to summon Gamabunta. Upon learning this he warned Naruto that it would be a big mistake to summon his father to the middle of the ocean, since toads are freshwater creatures.

Three-Tails Arc
Although he did not have his Part II début until much later in the manga, Gamakichi appeared sooner in the anime adaptation. Noticeably, Gamakichi was not yet as big as he would be in his manga debut, by which time he would be big enough for Naruto to stand on his head. In his anime debut, Gamakichi was easily big enough for Naruto to stand on his back.

When Naruto proved incapable of synchronising with Gamariki to learn collaboration techniques, Naruto decided to summon Gamakichi and Gamatatsu, as he had worked well with them before. After successfully synchronising with them, Naruto learned that neither of them had any skill in Water Release technique. With Naruto's help and lessons from their father, Gamakichi teaches the basics of Water Release to Gamatatsu.

Later, when Team Yamato found it impossible to break through Guren's crystal barrier via conventional means, Naruto summoned Gamakichi and Gamatatsu to help. Gamakichi kept Gamatatsu focused by warning him that he wouldn't get any snacks if he didn't focus on the task at hand. This enables Gamatatsu to break through the barrier, after which they return to Mount Myōboku. To their annoyance, however, Naruto keeps summoning them again, both to combat Team Guren and the Three-Tails. While fighting the latter, Gamakichi pointed out that their Water Release technique would be ineffective against its own water-based abilities. Naruto lamented the fact that they had no Fire Release technique at their disposal to evaporate the beast's water, but Gamakichi pointed out that he could use fire release and together with him using the Fire Release: Flame Bullet technique, they were able to perform the Wind Release: Toad Oil Flame Bullet.

After sending Gamatatsu back briefly to Mount Myōboku to bring back a stomachful of toad oil, Naruto, Gamatatsu, and Gamakichi combined their techniques to create the Wind Release: Toad Oil Flame Bullet. The resulting inferno drove through the Three-Tails' water attack and had the turtle demon fleeing under the lake's surface. Once the Three-Tails had been overcome, Gamakichi and Gamatatsu went back home.

Invasion of Pain Arc
Gamakichi made his Part II début in the manga when Naruto was informed of Jiraiya's death. He was later present during Naruto's senjutsu training having summoned Naruto to Mount Myōboku and later watched as he trained under Fukasaku. He was summoned again during Pain's attack on Konoha, where Naruto instructed him to get Tsunade to safety. He stayed with Sakura whom he had brought Tsunade to, laughing when the Deva Path starts running away to use Chibaku Tensei, thinking Naruto has scared him off. Sakura reprimanded him however, reminding him of the danger with Naruto and that they needed to use this opportunity to save Hinata Hyūga who had been badly injured. He is later seen with the other villagers congratulating Naruto on defeating Nagato.

Ten Tails Revival Arc
When Naruto, Sakura, and Sasuke simultaneously used the Summoning Technique, Gamakichi appeared alongside Aoda and Katsuyu. He showed a big improvement in size, looking a lot like Gamabunta, with a cigarette in his mouth.

Trivia

 * Gamakichi's name means "Propitious Toad".
 * In the English version, Gamakichi spoke in a New York accent. This could be a similar allusion to Gamabunta speaking in a Hiroshima dialect in the Japanese version, as both dialects are associated with gangsters.