Pokémon Red and Blue/Pallet Town

Choose your Pokémon
You can wander around and look for Professor Oak all you like, but you won't find him until you try to leave town.

Back at the lab, he'll give you a Pikachu in the Yellow version, or your choice of three other Pokémon in the Blue and Red versions.

Choose carefully: Not only will the Pokémon you pick be your strongest ally for the next few hours, but it will determine which Pokémon your rival picks as well.

Your rival awaits...
When you head for the exit, you'll be confronted by your rival (names Gary in the TV show) who's eager to test out his Pokémon in combat.

While Pikachu vs. Eevee is an even fight in the Yellow version, people playing Red or Blue will have a tougher match ahead of them, since your rival has shrewdly chosen the Pokémon that has an advantage over yours. Fortunately, your rival isn't mush of a fighter, and wastes time with defensive techniques like Growl and Tail Whip instead of just choosing the attacks and going for the quick K.O.

If you lose, though, no big deal: All you miss out on is your rival's 175 and a bit of EXP. And you'll get plenty of opportunities for a rematch.