Stephen Hawking Narrates 'The Big Bang Theory' Theme Song

"The Big Bang Theory" writers and cast packed a few delightfully nerdy surprises at Comic-Con, including a pre-taped recording of Stephen Hawking reciting the show's theme song.

Hawking, of course, has been referenced numerous times on the CBS series, and in one episode befriended main character Sheldon (Jim Parsons) via game "Words With Friends."

"When I'm not playing Words With Friends with Sheldon, I like to think about the universe," Hawking said from a remote office decorated with a "Big Bang Theory" banner and movie poster for "Hawking."

"Many people find the universe confusing — it's not. For example, the Big Bang Theory, here it is in 17 words."

Watch the clip:

And here's the original version of the theme song:

Previously, Hawkings made a fifth season cameo as his inimitable, clever self.

Watch his interaction with a starstruck Sheldon:

Hawking's opener was followed by a season six highlights reel and panel with writers Steve Molaro and Bill Prad, moderated by actress Melissa Rauch, who plays Bernadette.

During the Q&A, a fan cosplaying as Princess Leia disguised as the bounty hunter Boushh, stepped up to the mic and revealed himself as Johnny Galecki.

Johnny Galecki just showed at the #sdcc Big Bang Theory panel in a Star Wars costume as a surprise pic.twitter.com/ZZuIz5c7tG

— Emily Zemler (@emilyzemler) July 19, 2013

Here's a hi-res picture of the tricked out costume.

"The Big Bang Theory" returns to CBS on September 26.

"The Big Bang Theory" returns to CBS on September 26.