'Big Bang Theory' First Look: Katey Sagal and Jack McBrayer Make Their Debut

The TV vets play Penny's mom and brother, respectively.
'The Big Bang Theory'

The Big Bang Theory viewers are about to see a whole new side of Penny (Kaley Cuoco).

The upcoming season 10 premiere of the CBS sitcom is set to introduce Penny's mom (Katey Sagal) and her brother (Jack McBrayer), and The Hollywood Reporter has a first look at their highly anticipated series debut below.

In the premiere, titled "The Conjugal Conjecture," Penny's anxiety-ridden mother, Susan (Sagal), and drug-dealing brother, Randall (McBrayer), arrive for Leonard (Johnny Galecki) and Penny's wedding ceremony. As seen in the photo, Penny's father Wyatt (Keith Carradine) also comes to town, making for a seemingly awkward family reunion.

In an interview with THR earlier this month, showrunner Steve Molaro teased that the wedding "may not be as conventional as planned" but called it a "sweet" ceremony.

"Despite all the weirdness going on around it, you still have Leonard and Penny, who still love each other, and those pockets of love find a way of bubbling through the tension," he said. "The other weddings have all been extremely charming in their own way, and this one doesn't disappoint."

The season premiere also features appearances by Breaking Bad alum Dean Norris, as well as by returning guests Christine Baranski, Laurie Metcalf and Judd Hirsch.

Sagal and McBrayer's castings were announced at San Diego Comic-Con. For Sagal, the gig marks a reunion with Cuoco, who played Sagal's daughter on the ABC sitcom 8 Simple Rules. Sagal most recently starred on FX's The Bastard Executioner and is set to appear on NBC's freshman drama This Is Us. McBrayer, best known for his role on 30 Rock, has more recently appeared on The Middle and New Girl.

The Big Bang Theory's season premiere is set to air Monday, Sept. 19, at 8 p.m. ET/PT on CBS.