The ninth installment of the intellectual comedy series The Big Bang Theory returns on Monday, Sept. 21, at 8 p.m. on CBS and this early, we are deluged with a slew of spoilers and rumors.

The producers of the sitcom told Entertainment Weekly's The Spoiler Room that that actress Laurie Metcalf will be returning to the show to reprise her role as Sheldon's mom, Mary Cooper. Metcalf debuted on The Big Bang Theory in 2007 when she appeared in the episode The Luminous Fish Effect. Metcalf later appeared in six other episodes, including Getting On and The McCarthys.

Also making his return in the series is Penny's (Kaley Cuoco-Sweeting) Keith Carradine on episode 3. Carradine was last seen (his only episode) in season 4 when he appeared on the episode titled The Boyfriend Complexity.

According to Christian Post, Mary Cooper is an over-protective mother who always shows up whenever Sheldon Cooper (Jim Parsons) is in trouble. But she is also known to have dropped by Sheldon's place just for a visit and keep up with his son. Mary Cooper recently meet Leonard Hofstadter's mom, Beverly, when both women dropped by to celebrate with their son's physics award.

Mary Cooper's visit is expected as he broke up with girlfriend Amy Farrah Fowler (Mayim Bialik) in the season finale of season eight, via a Skype call. Mary is expected to provide some comfort to her son's heart ache in the coming season.

award. In the last episode of season eight, it can be remembered that Sheldon went through a bad heartbreak after his girlfriend Amy broke up with via a Skype call. It seems like Mary's return next season has something to do with her son's heart issue. Hopefully, she will be there to console Sheldon.

Carradine too has some comforting mission to do. Her daughter Penny is looking for some family support after eloping with Leonard to Las Vegas and finding out that he kissed another woman.

All the Dreams Came True for Penny

Cuoco-Sweeting is very excited for the upcoming season 9 of The Big Bang Theory. The 28-year-old actress told ET that the upcoming season of the long-running comedy is "off to a great start."

"Between Leonard and Penny... All the dreams came true for me," she hinted. And added,

Mayim Bialik also told ET during the Comic-Con in July, that The Big Bang Theory is  "the show about people who come to Comic-Con." She added, "We're not like those other shows. We're not here because we have that following, we're here because we're a show about that following."

The Big Bang Theory Season 9 will premiere on Monday, Sept. 21, at 8 p.m. on CBS.