19. The Body Switching Has An Actual Mathematical Solution
The solution to all the body swapping in The Prisoner Of Benda may seem painfully obvious (throw two people in and you can just cycle around until it's right) but with some pernickety fans the writers didn't want to take any chances, so created a mathematical theorem to prove it.
The Futurama Theorem (imaginative name there) was made by Ken Keeler, one of the show's writers (and a PhD in applied mathematics). You can see it on a screenshot of the episode above, but it's not as complicated as it seems; the maths is actually is pretty logical. The worrying thing is that the fans are so petty they'd have questioned this.
If only the writers had some way to highlight their ridiculousness. Actually they did, as you'll see next.