Things You'll Need
Instructions
In Pokemon Stadium, select the Master Ball division and enter the R-2 Prime Cup.
Create your team. Make sure you include your Pikachu from Pokemon yellow. Insert your Pokemon Yellow cartridge into your transfer pack and transfer your Pikachu to Pokemon Stadium on your Nintendo 64. Do not register your team. Make sure not to use a Pikachu rented from Pokemon Stadium.
Complete the Prime Cup in the Master Ball division using your team. Make sure Pikachu is always on the team--if he is absent in a single battle, you won't be able to acquire the Surf skill.
After you've acquired Surf Pikachu in Pokemon Stadium, load him back into your game boy and go to the Surf Hut in Route 19. You will now be able to play the Surf mini game.