In JN026, Goh discovered that Magikarp had grown very fat over its time at the Cerise Laboratory. To fix this, Goh trained Magikarp to compete in the Magikarp High Jump Tournament. During the tournament, Magikarp was able to make it to the semifinals, where it defeated Koi Kingen's Magikarp with a jump of 21.02 meters, breaking Goh's personal record in the process. In the finals, it competed against Kasuking's Shiny Magikarp. Before the finals began, Magikarp was revealed to have had two immensely heavy weights on its back fin. With the weights gone, it jumped so high it didn't come back. As such, its jump could not be measured, losing Goh the tournament. At the end of the episode, it crashed back down on Ash and Goh while they were on Slowpoke Island.
In JN031, Magikarp, alongside Goh's Goldeen, befriended Nami's Feebas, nicknamed Hi-chan. It later helped Hi-chan learn how to swim and jump better.
Personality and characteristics
As a giant Pokémon, Magikarp is exceptionally larger and stronger than other members of its infamously weak species. Its Splash, a normally useless move on its own, allows it to jump so high it exits the atmosphere, and it can send opponents flying as it returns to the ground. Magikarp can be very motivated when it has a goal to strive towards.