CBS’s The Big Bang Theory focused on nerdy scientists and roommates Leonard Hofstadter and Sheldon Cooper and their interactions with their next door neighbor, Penny, and their equally nerdy friends, Howard Wolowitz and Raj Koothrappali. Over the course of 12 seasons, the show saw several new characters join the main cast. The most significant additions were neuroscientist and Sheldon’s eventual wife Amy Farrah Fowler, microbiologist and Howard’s eventual wife Bernadette Rostenkowski, and comic book store owner Stuart Bloom.
But before characters like Amy and Bernadette were introduced to the series, The Big Bang Theory had a different scientist join the group for a brief period: Leslie Winkle. However, after being a crucial part of the show for three seasons, she would disappear, leaving many wondering what happened to the character.
Portrayed by actress Sara Gilbert, Leslie was a physicist who was introduced in Season 1 as a potential love interest for Leonard. Feeling desperate in his search for Penny, Leonard attempted to build a relationship with Leslie due to her shared intellect. Although the two ended up in bed together, she later revealed that she only used him for sex and that she had no interest in being his girlfriend. Leslie would go on to appear several times throughout the first season, usually to antagonize Sheldon.
Leslie was promoted to main character status in season 2, despite being absent for several episodes. Much of her history revolved around her rivalry with Sheldon and Leonard’s failed attempts to start a relationship with her. She even began a brief “friends with benefits” relationship with Howard, only to unceremoniously dump him over the phone later in the season. After this, her character was written out of Season 3 almost entirely, and she only appeared in the season finale to once again rebuff Leonard’s advances.
After her brief appearance in Season 3, Leslie disappeared from the series and Amy and Bernadette became the main scientists on the show. Although the creators of the show never officially confirmed why Leslie stopped appearing, rumors indicate that her departure occurred because the producers could not generate enough stories for the character, she was written off the show. Since her time on The Big Bang Theory, Sara Gilbert has continued to work in television, going on to create, co-host and executive produce CBS’s The Talk and star in ABC’s remake of Roseanne and its spinoff The Conners.
After a six-year absence, Leslie would return to The Big Bang Theory for the show’s 200th episode, Season 9’s “The Celebration Experimentation.” When Sheldon’s friends decided to throw him his first birthday party in years, Leslie was a of the many invited to the party. After reconnecting with Leonard, she made a toast to Sheldon and said that despite her rivalry in the past, she wanted him to have a happy birthday.