Summary CBS quietly replaced Amy Farrah Fowler's mother in The Big Bang Theory, reflecting Amy's growing importance in the series. The show wanted to bring in someone who could play Mrs. Fowler repeatedly and chose Kathy Bates due to her existing relationship with creator Chuck Lorre. The recasting of Amy's mom had an impact on the show's narrative, allowing Bates to portray a domineering mother and wife during Amy and Sheldon's wedding.
CBS quietly made a small recast in The Big Bang Theory but never explained the change, leading fans to wonder, "Why did they change Amy Farrah Fowler's mother?" What was supposed to be a guest appearance for Mayim Bialik quickly became a regular gig as Amy became Sheldon's (Jim Parsons) romantic interest. As she transitioned to be a bigger part of the sitcom, The Big Bang Theory also established her background, including her familiar ties.
Given everything else happening with the rest of the Pasadena gang, The Big Bang Theory developed Sheldon and Amy's romance gradually. This worked since both were uncertain about how to tackle their growing attraction toward each other. They eventually started dating in season 4, and part of that was Amy introducing Sheldon to her mother via a video call. At that point, Mrs. Fowler was played by Annie O'Donnell, by the time Sheldon and Amy got married in The Big Bang Theory season 11, she was replaced by Kathy Bates.
CBS didn't make a big deal out of the recast, but The Big Bang Theory showrunner Steven Holland explained the reasoning behind it (via TVLine). When the show initially introduced Mrs. Fowler, Sheldon's future wife was still a newbie in the series, with limited involvement. After eight years, she had become a main cast member and an important player in the narrative, which meant that there was a chance to put more focus on Amy's individual story in The Big Bang Theory.
The sitcom wanted to bring in someone who can play Mrs. Fowler repeatedly if the narrative called for it and series creator Chuck Lorre already had an existing relationship with Kathy Bates, so they took the opportunity to bring her in. This explanation checks out as after her first physical appearance, Bates' Mrs. Fowler also appeared at the start of The Big Bang Theory's final season.
Despite running for more than a decade, recasting wasn't the norm on The Big Bang Theory. CBS was able to keep its core cast intact, as well as, its supporting ensemble for years. So, switching actors for Mrs. Fowler was a rare occurrence. Despite only appearing for only a few times, the recast actually had some impact on the sitcom's narrative. Bates' imposing presence allowed the show to depict the character as a domineering mother and wife, something that was prevalent in Amy and Sheldon's wedding. The Big Bang Theory's final season leaned on it as Mrs. Fowler tried controlling Mrs. Fowler, played by Teller, who recently made a guest appearance on Young Sheldon playing a different character.
Since The Big Bang Theoryabruptly ended after season 12, unfortunately, the sitcom wasn't able to bring Bates' Mrs. Fowler more. She could have joined the ranks of Laurie Metcalf's Mary Cooper and Christine Baranski's Beverly Hofstadter as the most notable mothers in the series. Given Amy's guest appearances in Young Sheldon, however, perhaps the CBS prequel can also find a way to feature Bates as Sheldon's mother-in-law.
Recasting characters on sitcoms is something that has happened for decades and many of them are pretty memorable from Harriet Winslow on Family Matters to Vivian Banks on The Fresh Prince of Bel-Air to Laurie Forman on That '70s Show. However, The Big Bang Theory's biggest change is actually one that fans never got to see. In the unaired pilot, Penny was actually Katie, played by Amanda Walsh. It wasn't quite clicking so they recast Penny to Kaley Cuoco and made some changes to the character, which resulted in The Big Bang Theory officially getting greenlit.