Get Amnesia Psyduck
Get all 151 Pokémon in the hall of fame.

Get Surfing Pikachu
Complete the game.

Get Talking Pikachu
Name your Pikachu 'BLACK' in the yellow version of Pokémon, then upload it to Pokémon Stadium.

Get Surfing Raichu
Get a Raichu that knows SURF. It will put its tail under itself and use it as a surfboard.

Go to: Pokemon Stadium Info Page | nGaming Home Page.