Duke Nukum

The 2.0 name of the original "Duke Nukem" (the first game) in order to avoid a lawsuit with the Captain Planet cartoon show. However Apogee (Today 3D Realms) learned that the name was not copyrighted so they registered it and used it for all future titles.

Gamer 1: I purchased a game called Duke Nukum!
Gamer 2: Did you mean "Duke Nukem"?
Gamer 1: No, it's Duke Nukum.
Gamer 2: Porably a bootleg game.