Mayim Bialik is probably best known for two roles: Blossom on "Blossom" and Amy Farrah Fowler on "The Big Bang Theory." According to an oral history of Chuck Lorre's popular CBS sitcom, Bialik had some serious competition for the role of Amy ... and the actress who almost booked the gig ended up playing a recurring role anyway. So why did Bialik edge out "Garfunkel & Oates" actor Kate Micucci?

In Jessica Radloff's book "The Big Bang Theory: The Definitive, Inside Story of the Epic Hit Series," Lorre and his writer-producer Steve Molaro said that Bialik's real-life education helped her land the role; in 2007, Bialik earned a PhD in neuroscience from the University of California, Los Angeles (she also graduated from there in 2000 with a Bachelor's degree in the same field). As Lorre and Molaro told Radloff, that put Bialik over the edge.

"Chuck loved that she actually had a PhD in neuroscience," Molaro revealed. "It could have gone either way between Mayim or Kate, but because Mayim could bring an authenticity to the science and to the intelligence of the character, Chuck was like, 'I think that's so cool. Let's go with her.'"

Not only that, but Lorre said that Bialik felt like the right choice because her interpretation of Amy bore such a stunning similarity to Jim Parsons' lead character Sheldon Cooper -- which is exactly what they wanted. As casting director Ken Miller recalled, "Chuck said, 'You know, we're looking for a female version of Sheldon,' and Mayim goes, 'I got it.' She knew exactly what she was going to do with the character."