Sagal also played Cuoco's mom on '8 Simple Rules.'
Hours after Friday's Big Bang Theory panel at Comic-Con revealed Katey Sagal will be playing Penny's mother, "Susan," on the hit CBS comedy, Kaley Cuoco has weighed in about how thrilled she is at the casting.
While Cuoco was absent from the Comic-Con festivities, she made sure to make her feelings on the casting known via Instagram, and it looks like the 30-year-old actress couldn't be happier to be reunited with her former 8 Simple Rules TV mom.
WATCH: 'Big Bang Theory' Welcomes Katey Sagal and Jack McBrayer as Penny's Family Members
"Yes yes yes yes !!!" she posted to Instagram on Friday, along with a throwback pic of herself and Sagal. "Once my tv mom, always my tv mom ? love you@kateylous !!!!! #fullcircle."
Cuoco's Big Bang crew is also excited about the casting, as they told ET shortly after the news was released.
"There will be a little reunion there, which we're excited about," Executive Producer Steve Molaro told ET's Kevin Frazier. "She's going to be a little bit of a neurotic character because she's spent her life with her troubled son, Randall, who has been in and out of jail and has had some issues with dealing drugs. So we're going to start to dive into that."
Melissa Rauch made it clear she was also very… excited. "I'm very excited! I just found about this casting news the other day, and I was so excited," she exclaimed. "And Jack McBrayer playing Penny's brother is so exciting!"
WATCH: 'Big Bang Theory' Star Says Next Season Could Be Their Last
But while Cuoco's clearly delighted to have Sagal and McBrayer on set, the long-running series also getting a couple cast members she’s not too thrilled about -- babies!
See more in the video below.