The complete Pokemon RBY pokedex, part 12

Pokémon Name: Magikarp
Type: Water
Classification: Fish Pokemon
Pokédex Number: 129
Ability: Swift Swim
Dream World ability: Rattled
Useful Attacks: Flail
Location Found:
D/P/P/HG/SS: Fishing with Old Rod just about anywhere
HG/SS: Pokewalker - Stormy Beach, Warm Beach, Winner's Path
B/W: Marvelous Bridge (buy from Magikarp salesman)

The ultimate in useless Pokemon. Your reward for putting up with this joke? Gyarados, one of the most well-known creatures in the series.

Evolution: To Gyarados at 20