An upcoming Big Bang Theory oral history claims that actress and fan favorite Kaley Cuoco almost didn't land a major role at all. According to the book, the pilot's intended female lead, "Katie," was the polar opposite of Cuoco's Penny. As opposed to being a Midwestern optimist, Katie was "cynical, down on her luck, and off-putting," as stated in a The Hollywood Reporter article dated October 6.

Who was waiting to play Katie, by the way? Cuoco tried out for the part, but she wasn't awarded it because she was too chirpy. Instead, Marisa Tomei, an actress who was applying for the role, read with Jim Parsons.

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"I read with Marisa Tomei," Parsons shared in the book. "I remember going to the snack room after we were done and telling [casting directors] Ken [Miller] and Nikki [Valko], 'I've never been in someone else's audition before!' And they said, 'Well, she was kind of really auditioning you.' And I went, 'Oh, that makes sense.' But oh my gosh, what a different world that would have been."

Tara Reid from American Pie and Elizabeth Berkley from Saved by the Bell both applied for the position. However, Amanda Walsh ultimately landed the role of Katie when another actress, Jodi Lyn O'Keefe, attempted to play the part at a table read but failed. According to Valko, O'Keefe was deemed to have brought a "darkness" to the role that didn't fit.

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The first pilot was eventually shelved and redone sans Katie and Gilda. The original pilot also included Iris Bahr in the part of "Gilda," a colleague scientist with feelings for Johnny Galecki's Leonard who had had sex with Sheldon at a Star Trek conference.
 
The Big Bang Theory: The Definitive, Inside Story of the Epic Hit Series by Jessica Radloff, a forthcoming oral history, has also disclosed other behind-the-scenes details about the show. Galecki and Cuoco dated covertly from 2008 to 2010, and in the new book, they discussed their relationship.

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"All the scenes up until we actually got together in real life, it was obvious there was always something there," Cuoco shared. "There was chemistry, and we were crushing on each other. That was the whole first season until we actually got together for real."