• ''The Big Bang Theory'' stars Kaley Cuoco-Sweeting,  Jim Parsons, Johnny Galecki, Simon Helberg, Kunal Nayyar, Melissa Rauch  and Mayim Bialik.

''The Big Bang Theory'' stars Kaley Cuoco-Sweeting, Jim Parsons, Johnny Galecki, Simon Helberg, Kunal Nayyar, Melissa Rauch and Mayim Bialik. (Photo : Reuters/Mario Anzuoni)

Two parents are set to return in "The Big Bang Theory" season 9, which will premiere on CBS on Sept. 21. These are the father of Penny (Kaley Cuoco-Sweeting) and the mother of Sheldon (Jim Parsons).

"The Big Bang Theory" season 9 producers told Entertainment Weekly that Laurie Metcalf will reprise her role as Sheldon's mom in the first episode while Keith Carradine will reprise his role as Penny's dad in episode 3.

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Metcalf made her "The Big Bang Theory" debut in the 2007 episode titled "The Luminous Fish Effect" and returned in six other episodes before "The Big Bang Theory" season 9 episode 1. She also starred in several TV series including "Getting On" and "The McCarthys."

On the other hand, "The Big Bang Theory" season 9 episode 3 will be Carradine's second episode in the CBS show, his first being the 2010 episode titled "The Boyfriend Complexity." He also starred in "Fargo" and "Madam Secretary" and is currently filming "A Quiet Passion."

With Cuoco-Sweeting and Parsons, "The Big Bang Theory" season 9 main cast also includes Johnny Galecki as Leonard, Simon Helberg as Howard, Kunal Nayyar as Raj, Melissa Rauch as Bernadette and Mayim Bialik as Amy.

In other news, Bialik recently revealed that she was widely criticized for taking a trip to Israel where she visited a friend in the Israel Defense Forces. She Fox News, "That's what's amazing. (I was slammed) simply by going to Israel this summer and saying nothing more than, 'I've gone to Israel.'"

"I got the same amount of hatred and threats and anti-Semitism for actually making a statement trying to support people whether I like it or not are serving in an army," the Jewish actress added.