Pokémon Stadium
The first Pokémon game to feature 3D, made for the N64.
In the game's stadium you defeat trainers to win the several
cups, in the Gym Leader castles you defeat the trainers and
finally the Gym Leader to win badges.
After this all Mewtwo appears and you fight him in a 6-to-1 battle.
You can also visit Oak's lab (to check your Pokédex and various other things) And play a total of nine mini-games among which, Sushi-go-round, Ekans'hoop hurl and seven more!
Connect your Pokémon cartridges for even more options and things to play with, using the transfer pak.