Christmas Message
If the date is 12/25 and you load up your game a "Merry X-mas!!" message will appear.

Shower Scene
Finish game in Normal Mode, then start a new game in Hard Mode. When you get to Laura's room, press A to see Laura's shower scene.

New Years Message
Set your Saturn's clock to 1/1 and load your game. The Voice Recorder will say Happy New Years.

Zero Enemies
In Laura's room enter: a, l, c, x and there will be no enemies