Bulbasaur was assigned National Pokédex number 001 in the first generation.
Bulbasaur is one of the three Pokémon offered to new players at the beginning of Pokémon Red, Green, Blue, and their related versions. It is a dual-type Grass and Poison Pokémon with a plant bulb growing on its back. The bulb develops as Bulbasaur grows and eventually leads to its evolutions, Ivysaur and Venusaur.
The National Pokédex numbering begins with Bulbasaur and ends with Mew at number 151. That ordering is not simply a ranking of strength or popularity; it provides a consistent catalog for the original species. Later generations continued the numbering with new Pokémon.
Bulbasaur is sometimes confused with the first Pokémon shown in the anime or with Pikachu, the franchise mascot. Pikachu became the best-known Pokémon through the television series, but Bulbasaur is the first entry in the original Pokédex and one of the original starter choices.