Magikarp is one of the species of Pokémon creatures from the Pokémon media franchise—a collection of video games, anime, manga, books, trading cards, and other media created by Satoshi Tajiri. As do all Pokémon, Magikarp fight other Pokémon in battles (for specific values of "fight") central to the anime, manga, and games of the series.
Magikarp is a red fish widely treated as a joke due to its abysmal combat ability, learning only three moves (one of which has absolutely no effect) before it evolves into Gyarados at level 20. Ironically, it can be fished out of any body of water in Generations 1, 2, 3 (FireRed/LeafGreen) and 4 with an Old Rod. Shiny Magikarp are gold, but no less worthless.