Due to old game mechanics, the Master Ball had a 1/255 chance of failing in the original games.

Mew was added without Nintendo's awareness, which was especially risky because the debugging program had already been uninstalled.

There were originally 190 Pokémon, but thirty-nine were moved to future generations. This explains MISSINGNO.

A female trainer was meant to be introduced in first-gen, but there wasn't enough space.