'Big Bang Theory' Welcomes Katey Sagal and Jack McBrayer as Penny's Family Members

The Big Bang Theory is introducing members of Penny's family!

The Big Bang Theory
is introducing members of Penny’s family!

Katey Sagal will reunite with former co-star Kaley Cuoco on television’s biggest comedy, playing Penny’s mother, "Susan," executive producer Steve Molaro announced during Friday’s Comic-Con panel.

30 Rock
’s Jack McBrayer has also been cast as Penny’s drug-dealing brother, "Randall," it was revealed at the panel.

Sagal and McBrayer will make their Big Bang debuts in the season 10 premiere.

WATCH: 'Big Bang Theory' Star Says Next Season Could Be Their Last

“I talked to Katey on the phone,” Molaro said of Sagal’s casting. “And she said, ‘I’m always ready to play Kaley’s mom!’”

McBrayer made a surprise appearance at the end of the session, joking that he’s only been to jail “recreationally.” (Penny’s brother is jail-bound.)

“I look real good in orange. I’m really good at making new friends,” McBrayer joked.

Sagal and Cuoco starred as mother and daughter for more than 75 episodes in the ABC comedy, 8 Simple Rules, from 2002-05.

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As for whether Big Bang is nearing the end of its run, Molaro was coy.

“I’m not going to tell you,” he said. “There’s been a few thoughts that have floated around but nothing concrete. We don’t really know how long the show is going to go on for. It’s a little early to be thinking about [that].”

Are you excited by Katey Sagal and Jack McBrayer’s castings as Penny’s mother and brother? Sound off via Twitter by tagging @etnow!

The Big Bang Theory
returns Sept. 19 on CBS.