Penny's Mother and Brother Have Arrived -- Watch the Awkward Family Reunion! 

Playing EXCLUSIVE! 'The Big Bang Theory': Penny's Mother and Brother Have Arrived -- Watch the Awkward Family Reunion!

After nearly ten years of vague stories and M.I.A family members, we’re finally going to meet Penny\'s mother and brother in the season 10 premiere -- and only ET has your exclusive first look!

In our sneak peek above, Kaley Cuoco reunites with her

co-star, Katey Sagal, who is once again playing the role of her on-screen mother. Sagal and Cuoco starred as mom and daughter for more than 75 episodes in the ABC comedy from 2002-05.

\'s Jack McBrayer also makes his Big Bang debut as Randall, Penny\'s brother who has infamously been mentioned on the series as a drug-making criminal.

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

\'s season 10 premiere, which airs Monday Sept. 19 on CBS, is bringing everyone\'s families together to celebrate Penny and Leonard\'s wedding ceremony. (Fingers crossed this means we\'re finally going to learn Penny\'s last name!)

In the clip above, Penny and her dad, played once again by Keith Carradine, are sharing a beer and chatting about her success as a pharmaceutical sales rep, while anxiety-ridden Susan (Sagal) chastises Randall for not living up to his potential.

"Hey! She just sell drugs, I had to make \'em," Randall proudly quipped.

Back in July, McBrayer made a surprise appearance at

panel at Comic-Con and joked that, unlike his character, he’s only been to jail “recreationally,” but he looks "real good in orange."

premieres Monday, Sept. 19 at 8 p.m. ET/PT on CBS.

goodies? Press play on our exclusive clip below to find out how Kaley Cuoco defines "love."

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