"When I'm not playing Words With Friends with Sheldon, I like to think about the universe," reveals Stephen Hawking in a pre-recorded message for Comic-Con, in a surprise intro to Friday's Big Bang Theory panel.

Jim Parson's Sheldon met Hawking in "The Exact Obliteration" (6x06,) aired Nov 1, 2012.


He looks so different! Johnny Galecki dressed as a bounty hunter from Return of the Jedi to surprise fans at Comic-Con.