I started over a new game on my Leafgreen and chose Squirtle. I only chose Squirtle because I wanted to have an easy time at the beginning of the game until I got my next Pokemon. So I breezed through the game, beat Brock, and eventually arrived at Mt. Moon. I paid a ridiculous price for a Magikarp, and I have started to train it. It is difficult though since it knows no attacks, but oh well. It is currently at lvl 8.