Caterpie

Caterpie (Japanese: キャタピー Kyatapii) is a -type Pokémon introduced in Generation I.

Physiology
Caterpie is a worm-like Pokémon that is mainly green in color with a tan underside. Just below its head are four tiny legs that are used only for movement. On top of its head is a red, "y-shaped" antenna, which can be used to produce an odor used in self-defense, in case something tries to hurt it.

Special abilities
Caterpie has the ability Shield Dust, which negates all status effects that are side effects of other moves. When threatened, it can release a strong odor from its antenna, which it uses to ward off predators.

Evolution
Caterpie evolves into Metapod at level 7 and then Butterfree at level 10.

Leveling
Generation VI=

Generation V=

Generation IV=

Generation III=

Generation II=

Generation I=

Ash's Caterpie


Though Caterpie has quite a few cameos, the only time one of the main characters owned one was when Ash had caught a Caterpie in the episode Ash Catches a Pokémon, being the first Pokémon he ever caught. During the same episode, Caterpie evolved into a Metapod.

Trivia

 * Caterpie, along with Weedle, evolves faster than any other Bug type.
 * Caterpie shares the same species name with Wurmple called the Worm Pokémon.

Etymology
Caterpie's name appears to be based on caterpillar while its species appears to be a caterpillar evolving into a butterfly.