I remember an old adventure module for "Space Gothic" (a german hard scifi RPG from the 90s) which was build around a military robot research facility which go silent right at christmas.
When the player arrived they found the whole facility decorated for the Christmas party, Christmas songs playing from the speakers etc. But all people were dead, killed by projectile, laser, flamer etc.
Then while exploring the station they will be attacked by a military robot (aka an AHAV) decorated as Santa Claus.
Playing this was so much fun, because it was such a surreal combination. (our DM played Christmas songs throughout the whole evening...^^)