I vaguely remember seeing the eponymous Discovery Channel commercial some time ago and being delighted by it, enough to back up the TiVO and watch it again. Then xkcd did a version which delighted me also.
I went looking for the commercial today and found that youtube actually had a contest and listed the submissions. There are versions with different lyrics (e.g., Canada and the EU) and different images (e.g., every online gaming system or MMPORG you can think of). My favorite is a punk-rock version of the music, with lyrics and visuals according to the xkcd strip, but a close second has to be the Dr. Who version (with bonus Captain Jack appearances)!