Stephen Hawking returned to CBS' "Big Bang Theory" on Thursday night for a somewhat surreal cameo: The renowned physicist became locked in an intense game of Words With Friends against the notoriously competitive Sheldon Cooper.

Hilariously, Hawking turned out to be kind of a sore loser, giving up on the game until Sheldon let him win ... and then proving himself to be a sore winner too, by gloating over the victory.

Naturally, Leonard wasn't terribly sympathetic. But the other big news of the episode came from Penny. Our struggling actress/waitress decided to start taking a college class. Watch out, geeks -- there's a new brainiac in town.

"The Big Bang Theory" airs Thursdays at 8 p.m. ET on CBS.

TV Replay scours the vast television landscape to find the most interesting, amusing, and, on a good day, amazing moments, and delivers them right to your browser.

Related on HuffPost:

Loading Slideshow...
  • The Good Wife

  • 2 Broke Girls

  • Mike & Molly

  • The Big Bang Theory

  • Big Brother

  • Hawaii Five-0

  • How I Met Your Mother

  • Criminal Minds

  • Two And A Half Men

  • NCIS

  • The Mentalist

  • Person Of Interest

  • Elementary

  • CSI: Crime Scene Investigation

  • NCIS: Los Angeles

  • Blue Bloods

  • Survivor