"The Big Bang Theory" co-creator Chuck Lorre says Kaley Cuoco's character Penny took a few seasons to fully understand. "It's a cliched character: the dumb blonde, and we missed it," Lorre said during the first episode of "The Official Big Bang Theory Podcast.

Prior to Kaley Cuoco, actress Amanda Walsh was cast to play Katie, “a street-hardened tough-as-nails woman with a vulnerable interior.”

The Big Bang Theory may be defying the laws of TV mechanics with its storied success, but there’s one thing co-creator Chuck Lorre said the series “missed” early on with regard to Kaley Cuoco’s character Penny.