To get surfing pikachu you need a Nintendo 64 a pokemon stadium game a transfer pack and pokemon yellow go to gym leaders castle in pokemon stadium win against alll the gym leaders then continue and a new path will appear to the elite four go there you wil have to beat them in a row If you lose once you go straight back to loreli.

If you do beat them they will give you a pokemon it still wont be easy so far I only got 4 different pokemon.

Surfing Pikachu.

Dratini.

Bulbasaur.

Jigglypuff.

So good luck.