Pokemon Theme Song
The pokemon theme song was first featured during the original run of anime that started in 1996. This show helped to increase the popularity of pokemon and reinforce the idea of catching all of the pokemon. The characters in the show also showcased a lot fo different pokemon and adventures that could not be obtained through the games.
Pokemon Red
The art of this game features Charizard, Charmader's final evolution.
Pokemon Blue
The art of this game features Blastoise, Squirtle's final evolution.
Pokemon Yellow
The art of this game features Pikachue, which has become the symbol of pokemon as a whole.
Since 1996 there have been 8 different generations of pokemon. The newest being announced only this past February. Each game has new and different pokemon, but most also include pokemon from past games too. All of the games take place in a different region of the pokemon world and connect in some way. Each game also has similar features that run through each of the games. This has contributed to what is called the "Pokemon Formula". Each game has a crime organization, a pokemon professor to help you out, and multiple legendaries that you can catch in the game, usually featured on the box art for that specific game.