The Big Bang Theory co-creator Chuck Lorre is opening up about why it “took a while to figure out” Kaley Cuoco‘s character Penny on the hit sitcom.

Lorre, alongside Warner Bros. Television Group chairman and CEO Peter Roth, appeared on the first episode of The Official Big Bang Theory Podcast, where they looked back at the beginning of the Emmy-winning series, specifically the two pilot episodes.

Cuoco actually joined the series following script rewrites. They ultimately retaped the pilot episode with Cuoco as lead, following the first, unaired pilot, which featured two female leads, Katie (Amanda Walsh) and Gilda (Iris Bahr).