In the first few seasons of "The Big Bang Theory," Penny was an integral part of the CBS comedy's cast, but the lives of the nerdy male protagonists made up the show's focus. However, Mayim Bialik, who would play Sheldon’s girlfriend, Amy Farrah Fowler, was referenced subtly in the show's first season.
In the Season 1 episode "The Bat Jar Conjecture," Sheldon looks for someone to join his “Physics Bowl'' team. Raj suggests, "You know who's apparently very smart, is the girl who played TV's 'Blossom.' She got a Ph.D. in neuroscience or something."
Bialik played the titular character on "Blossom," a coming-of-age sitcom, which aired on NBC from 1990-to 1995. Bialik received her doctorate in neuroscience from the University of California, making her the only cast member on “Big Bang Theory” with an actual background in science.
Bialik also had chemistry with "Big Bang" co-star, Johnny Galecki, in fact his first on-screen kiss was on a "Blossom" episode in which he played Bialik’s romantic interest. "It might've been my first real-life kiss also," Bialik told Conan O'Brien in a 2016 cast appearance on his late-night show, during which they also re-enacted the kiss.