The fourth season of the American sitcom The Big Bang Theory aired on CBS from September 23, 2010 to May 19, 2011. Melissa Rauch and Mayim Bialik auditioned and were promoted to the main cast during this season as Dr. Bernadette Rostenkowski and Dr. Amy Farrah Fowler respectively.

Mayim Chaya Bialik is an American actress, author and former game show host. From 1991 to 1995, she played the title character of the NBC sitcom Blossom. From 2010 to 2019, she played neuroscientist Amy Farrah Fowler on the CBS sitcom The Big Bang Theory, for which she was nominated four times for the Primetime Emmy Award for Outstanding Supporting Actress in a Comedy Series and won the Critics' Choice Television Award for Best Supporting Actress in a Comedy Series in 2015 and 2017. Bialik shared hosting duties of Jeopardy! with Ken Jennings on a rotating basis between August 2021 and December 2023.