Recent research has revealed the presence of dragon DNA in this species of Pokémon.
This card was included in the Team Rocket expansion, first released in the Japanese Rocket Gang expansion. In an attempt to be helpful by adding a reference of what cards evolve from Magikarp, the English release of this card's Rapid Evolution attack actually limits which cards can be selected when using this attack. A more precise translation would have allowed players to search their deck for cards that evolve from Magikarp, such as Gyarados ex, that are not named Gyarados or Dark Gyarados.
The Rapid Evolution attack once allowed players to combo it with cards such as Recall to stack on as many of any combination of Gyarados and Dark Gyarados cards as they wished. A rule change was made in time for the Neo Genesis set that specifically forbade this kind of combo, deemed an "illegal evolution".