Bird type

Aside from the standard fifteen Pokémon types of Red/Blue/Yellow and the seventeen of Gold/Silver/Crystal, there is a another type, hidden in the programming. This type is named Bird.

The Bird type is quite enigmatic. Its attacks are physical, or would be if any existed. No attack is of the Bird type and no Pokémon is of the Bird type. There are no types super-effective or not very effective against it, nor are any types weak or resistant to it. It’s just… there.

Interestingly enough, Missingno. and 'M are partly Bird type. However, Bird never comes into play outside of glitches.

This type was never removed from the source code, and exists in all games up to and including Pokémon Crystal.

Most believe that “Bird” was the original name for the Flying type.