The Christmas Calendar widget is probably the weirdest Advent Calendar I've come across to date. Instead of showing a different part of the Nativity each day it will bring up a special Windows jokes, with 24 in total. Try clicking on a future date and the widget will show the picture of a cat warning you not to open up boxes before the given date.
Even if somewhat strange, the Christmas Calendar widget is on the whole pretty funny. Having an Advent Calendar on your desktop will also bring back some nice memories to some people. Also, as a widget, it really is quite unobtrusive and you can immediately close it once you've opened up the box for the day.
The Christmas Calendar widget is an original Advent Calendar with Windows jokes for each day.