Beat R1 Mode, and reload the game. In place of the title screen is a new one.
Register all 151 Pokemon in the Hall of Fame.
After beating the R2 Mewtwo, go to the Gallery. Scroll down
to ''Print'' and hold L and R. Print will become ''Bonus''.
Press A to view the game backgrounds, which can be printed
off at a Pokemon Snap station.
If you nickname your Pokemon in the Gameboy game and bring it into Stadium, it will have changed color depending on what you nicknamed it!
This has NOTHING to do with shiny Pokemon, because they were not invented when Stadium was released.
Possibilities range from an orange Pikachu to a seagreen Tentacruel.
If you beat Master Ball in PokéCup or Primecup
you will get dodou speed. This allows you to play your pokemon game in pokemon tower at X2 speed.