* Gastly sprites in Red, Blue, and Green have an error. Its black orb in the middle of its body is not present in said games. This was fixed in Yellow.
** Even though Yellow is a game made nearly the same time as Red and Blue, Gastly's back sprite was also fixed in Yellow, while all other Generation I Pokémon have the same back sprites for Red, Blue, Green, and Yellow.
* Gastly's prototype name was "Spirit".