YELLOW

In the beginning, Prof. Oak fights/captures a wild Pikachu, and gives it to you. Gary starts off with an Eevee Team Rocket is in!!! They have Meowth, Ekans, and Koffing (all of which evolve)

It's possible to catch wild Charmanders, Squirtles, and Bulbasaurs (like the show)

Cheats don't work in this version

Pictures of some Pokemon and Gym Leaders have been improved

You can print your Pokedex and Pokemon stickers via the GameBoy Printer

Pikachu follows you around (you can see him on the screen)

Follows the show more closely than Blue/Red

Pokemon evolve at different levels in the Yellow version

Some TMs won't work on the Pokemon that they used to work on in the Red/Blue version