ROTT holidays
 

Rise of the triad:
If you play the game before a major holiday (like on xmas eve)the game
kicks into holiday mode for the team picture/loading level screen.
The team will have xmas hats on and I think the game plays xmas music if I remember correctly.

You can also simply set the system time to the according date and the game will use the holiday mode.
There are other holidays also, if I remember correctly, when the game does special things, as on Halloween and Eastern.

I remember seeing this when younger, but never thought anything of it. I guess I was too occupied with killing people in the game hahaha