"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.

"We did the very clichéd, in the beginning, goofy blonde who says foolish things," Lorre says of the character Penny.

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