Katie was deemed a poor fit for the original Big Bang Theory cast due to her harsh nature towards Sheldon and Leonard, unlike Penny. Amanda Walsh, who played Katie, had minor roles before Tbbt and saw the show as a career-defining moment despite being ultimately replaced. Walsh, along with another actor, was cut from the show after the pilot reshuffle, ultimately leading to the beloved Tbbt cast viewers know today.

Actor Amanda Walsh, who was cast as the original female lead of The Big Bang Theory, has opened up up about her and her character, Katie, being cut from the show and replaced by Kayley Cuoco as Penny. In 2006, creators Chuck Lorre and Bill Prady pitched a new comedy pilot to CBS. Sadly, the show's initial iteration was rejected, forcing them to retool the pilot and resulting in what ultimately became The Big Bang Theory.

The original The Big Bang Theory...