Thursday's The Big Bang Theory found the guys excited to buy tickets for San Diego Comic-Con, the massive annual convention about comics and sci-fi/fantasy/horror movies and TV.

A huge part of the Comic-Con experience is cosplay, where attendees dress as their favorite characters. Sheldon (Jim Parsons) said that he was going to go as Albus Dumbledore (Michael Gambon) from Harry Potter. He mentioned it twice. But we never got to see the costume, since his friends all decided they weren't going to go to Comic-Con and presumably he isn't, either.

If he had mentioned Dumbledore once, it would have been a throwaway line. But he mentioned it twice. This breaks comedy's rule of three, where things that happen three times are funny and satisfying. Two is an awkward number that leaves an itchy sensation. There should have been three mentions of Dumbledore, and on the third reference we should have seen Sheldon in his Dumbledore costume.

A sitcom as traditional as The Big Bang Theory should know this.

If you wanted to see Sheldon as Dumbledore and were disappointed that you didn't get to, TVGuide.com can scratch your itch. Sheldon's Dumbledore cosplay would look a little something like this:

Your nightmares are welcome.

The Big Bang Theory airs Thursdays at 8/7c on CBS.

(Full disclosure: TVGuide.com is owned by CBS.)

Illustration by Michael Caso