Things You'll Need
Instructions
Complete the Gym Leader's Castle along with all 10 tournaments in "Pokemon Stadium." This will unlock a battle with the rare Pokemon, Mewtwo. Defeat him to unlock Round Two, or R-2, mode.
Press the "C-stick" on the Nintendo 64 controller to the right at the title screen, and then begin the game to enter R-2 mode. Complete the stages of the Stadium Mode until you reach the Master Cup.
Place your "Pokemon Yellow" cartridge into your Transfer Pack. Create an unregistered team from the Pokemon that you have; include a Pikachu in it. A rental Pokemon must not be used.
Select Pikachu to place it into your team each round, sending it into each battle. Do not use any continues, or else you will not be able to receive the surfing Pikachu.
Win all eight matches; you will then see a screen that shows a surfing Pikachu as an award. The Pikachu that you used for the battles will now know Surf.