Gamatatsu

is one of Gamabunta's children and Gamakichi's younger brother, and has a fixation with snacks.

Personality
Gamatatsu is portrayed as being even more simple and stupid than Naruto is or ever was. From his first appearance, Gamatatsu showed that he would choose snacks over someone's life; after Naruto was injured whilst fighting Kabuto Yakushi, he asked, "Hey Gamakichi, do we have to wait for the kid to croak till we get snacks, 'cause I'm getting hungry." However, in the filler arcs, Gamatatsu showed that he does care about Naruto's life, as he was ready to rescue him before Gamakichi talked him out of it. Whilst being naive and childishly stupid, he does sometimes make use of his natural curiosity to help Naruto solve puzzles (like the mystery of the Ghost Warrior in the Bird Country Mystery arc).

Gamatatsu's obsession with snacks is so great that he waited a year since his first summon for the snack he had been promised, even though he still didn't get it. He is always hungry and asking his summoner for snacks, and often gets confused by unusual predicaments, in which he counts on his "big brother Gamakichi" to help him with. In the English anime, his voice is jocularly high. He also openly refers to Gamabunta as "daddy", which the older toad either chooses to ignore or simply doesn't mind.

Gamatatsu seems to lack a sense of danger. When Orochimaru summoned Manda, Gamatatsu was too busy saying hello to his father to notice that the giant snake was staring at him. The young toad did not seem frightened in the least until Gamakichi told him to run. However, this fearlessness may also have been due to his titanic and overprotective father's presence, or his lack of a sense of endangerment.

Search for Tsunade arc
Gamatatsu was accidentally summoned by Naruto Uzumaki during a battle with Orochimaru in an attempt to compensate for Jiraiya's failed summoning.

Bird Country Mystery arc
Gamatatsu made a short appearance in the Land of Birds arc when Gamakichi and Naruto needed him. Despite Naruto thinking he would be useless, Gamatatsu, using his curiosity, found a kite that was a clue about how the Cursed Warrior flew. Later, he went down a dark tunnel with Naruto and Gamakichi, and was caught by the Daimyo and his guards. These events have led Naruto to believe that Gamatatsu can sometimes be helpful.

Sea Country arc
He was summoned again with Gamakichi by Naruto in the Land of Sea.

Three-Tailed Beast arc
Gamatatsu has yet to appear in Part II of the manga. In the anime, when Naruto proved incapable of synchronizing with Gamariki for combination jutsu, Naruto decided to summon Gamakichi and Gamatatsu, as he had worked well with them before. Naruto was amazed at how much they had both grown, as they were now bigger than him, which Gamatatsu claimed to be due to all the snacks they had eaten. Naruto then learned that neither Gamatatsu or Gamakichi had mastered water-based abilities like their father, but decided to continue working with them regardless, since Naruto found it more preferable to working with Gamariki.

Deciding to try and learn water-based techniques, Gamatatsu began getting trained by Gamakichi with what appeared to be the basics of water chakra learned from their father. After several failed attempts at using water chakra, which involved using already existing water stored in Gamatatsu's mouth, he finally managed a powerful water blast. Later, when Team Yamato found it impossible to break through Guren's crystal barrier via conventional means, Naruto summoned Gamakichi and Gamatatsu to help. Gamatatsu used his newly learned water blast to break through Guren's crystal, and subsequently helped rescue Hinata. After their job was finished, they returned home.

Unfortunately, Naruto repeatedly called him and his brother back to aid him during the mission, an example of this being when Naruto called the two brothers to aid him in crossing a lake and defending the team who were trying to seal the Three-Tails.

Quotes

 * (To Gamabunta) "How you doing, Daddy?"
 * "Can I have a snack?"
 * "This is the first time anyone's ever summoned me! I'm finally getting a chance to shine!"
 * "Hi everybody!"