It was originally a Spearow that Ash encountered on his way to Viridian City, but couldn't capture. Later, when it evolved into a Fearow and was terrorizing Pidgey and Pidgeotto, Ash attempted to capture it but failed and left his Pidgeot to guard them.
In the Electric Tale of Pikachu manga, Ash captured it early-on, as his Pidgeotto abandoned him early on. It quickly becomes his primary -type Pokémon.
|Mirror Move||Haunting My Dreams|
|+ indicates this Pokémon used this move recently.*|
- indicates this Pokémon normally can't use this move.