A 10-part HBO Max spin-off to The Big Bang Theory expands on that long-running sitcom by following a quartet of its characters. Every episode offers a new multiverse — and surprising cameos.

The 'Stuart Fails to Save the Universe' producers explain how Episode 2's surprise Kaley Cuoco cameo as an alternate Penny happened.

‘Stuart Fails to Save the Universe’ episode two sees another major ‘Big Bang Theory’ cameo