The apparent difference in the rate of time perceived by someone taking a dump compared to the rest of the world. (For every minute you think you've been sitting on the toilet, 80-100 seconds have actually gone by.) The Turd Law rarely holds up to empirical measurement, and is therefore considered by the scientific community to be a big load of crap.
Boss: "If you weren't in there droppin' a deuce for so long you might be done your work by now."
Me: "I was in there for five minutes. Six tops."
Boss: "More like 15 or 20…"
Me: "Well I'll be damned. I just proved the Turd Law of Relativity."