Alright, this is something right up my alley - figuring out Yoda's peak power output using math and physics: http://what-if.xkcd.com/3/
It's actually not that much.
What's great is that you found that new sub-sites of XKCD.
There's only the 3 of them... so far.
quite like the "guessing on the SAT" one:
http://what-if.xkcd.com/2/
Quote
...the odds of acing the SAT by guessing are worse than the odds of every living ex-President and every member of the main cast of Firefly all being independently struck by lightning ? on the same day.