Starter Pokémon

One of the consistent aspects of the Pokémon games – spanning from Pokémon Red and Blue on the Nintendo Game Boy to the Nintendo DS game, Pokémon Diamond and Pearl – is the choice of one of three different Pokémon at the start of the player's adventures; these three are often labeled "starter Pokémon". Players can choose a Grass-type, a Fire-type, or a Water-type. For example, in Pokémon Red and Blue, the player has the choice of starting with Bulbasaur, Charmander, or Squirtle. The exception to this rule is Pokémon Yellow (a remake of the original games that follows the story of the Pokémon anime), where players are given a Pikachu, an Electric-type mouse Pokémon, famous for being the mascot of the Pokémon media franchise; in this game, however, the three starter Pokémon from Red and Blue can be obtained during the quest by a single player, something that is not possible in any other installment of the franchise.
Another consistent aspect is that the player's rival will always choose as his or her starter Pokémon the one that has a type advantage over the player's Pokémon. For instance, if the player picks a Grass-type Pokémon, the rival will always pick the fire-type starter. Of course, the exception to this is again Pokémon Yellow, in which the rival picks an Eevee, but whether this Eevee evolves into Jolteon, Vaporeon, or Flareon is decided by when the player wins and loses to the rival through the journey.