Extraneous data accidentally included

In game production, disks, EPROMs, flash RAM chips, and other rewritable media often get reused to save costs. Portions of the data on this media may not be entirely overwritten with the data from newer projects. If this media is then used as a master copy for production, the older data is included in the production copies. This data is probably unrelated to the final game, does not impede the function of the game, and is generally inaccessible to most consumers who don't have special tools to access the supposedly overwritten data.