An error trap, error trapper, or simply a trap, for the purpose of this wiki, is a preventative measure used to avoid the effects of glitches, such as freezes or to prevent cheating.
A common example of an error trapper is the infamous "This program has caused an illegal operation" message in Windows 95 and 98.
?????????? is an example of an error trap in Generation III. Most invalid Pokémon use this name when they are on the opponent's side, and have a "? mark in a circle sprite".