Luigi has been hiding in a Dreamcast game prototype for 21 years

Luigi is showing up everywhere these days, and his latest unexpected appearance is in a recently uncovered Sega prototype from 2000.

The prototype in question is of Sega GT for Dreamcast, and as far as anyone can tell, Luigi does not appear in the final version. You wouldn't expect him to, since Sega and Nintendo were still fierce competitors back in 2000. Nonetheless, games preservationist Comby Laurent found the taller, greener, and weirder of the two Mario brothers holding a checkered flag and stopwatch in the prototype, as spotted by Kotaku.

Luigi appears in an unreleased race named "sonygt2," which itself seems to be a reference to an even more direct competitor: Sony's Gran Turismo 2, which came out less than a year before this Sega GT prototype was made. Given the fact that nothing like the map or its plumber cameo appear in the final game, it seems safe to assume that they were created solely as an in-joke and removed before full release, with the assumption that no one outside the development team would ever be the wiser.

The Sega GT prototype was released along with hundreds of other Dreamcast and Xbox games as part of Project Deluge, a coordinated effort from game preservation group Hidden Palace. Other Dreamcast prototypes rolled into the release include 4 Wheel Thunder (then called Offroad Thunder), Deep Fighter, Illbleed, and the cult classic Jet Grind Radio. There was even an unreleased English localization of mahjong game Shanghai Dynasty, which Activision was apparently working on before it was cancelled.

Find more retro thrills in our guide to the best Dreamcast games of all time.