I like what Dungeon Keeper 2 did with the real world. It watched the clock and had special messages that it played at certain times. Midnight was always "It is the witching hour. Curses are half price." Every hour after that suggested it was time to go to bed.
What?! I didn't know that!!! *runs installing Dungeon Keeper 2* oh cant' wait untill midnight! I never played at night, that is.
While you're at it, look out for the hidden secret level. It only appears when your up to level 12 (I think it's 12? It's after the one where you have to catch the lord as he runs from one end of the map to the other.) There is a moon floating above the land and it's only there inbetween these two missions. I thought it only came on a full moon, but it seems to be mission related.
Taken from a FAQ for a DOS RPG,
Ancient Domains of Mystery:
Q: Why are all the characters I create cursed?
A: Have a look at your clock. It's probably Friday the 13th.
