Fan disc
Appearance
A fan disc is usually a released by a game company after the successful launch of a game. The content adds new images, music and other media and usually extends the game's time line by adding in a new shorter game, however they are not considered true sequels. The creation of a fan disc usually signals the end of a series.
Eroge visual novels such as Popotan are good examples of games that usually get fan discs. Sometimes such as Come See Me Tonight series, a fan disc is made as a compilation of the two separate, but similar games to link them.
These extensions are generally not translated. There have been no known commerical translations and only a few fan-translated attempts, such as Tsukihime's PLUS-disc translation by Mirror Moon.