Yes, that's Keith Carradine on The Big Bang Theory. He's played the character of Penny's dad.
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Leonard tries to keep an affair secret from Sheldon on "The Irish Pub Formulation." This is a scene from that episode.
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A flashback to when Leonard first moved in with Sheldon and they signed the roommate agreement.
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Before there was Leonard, there was an even angrier roommate. Angry enough to write "Die Sheldon Die."
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A flashback to the nerds when they first met playing Gamecube together.
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Sara Gilbert is seen here on The Big Bang Theory. She plays the character of Leslie.
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Penny and Leonard come outside to see Sheldon trapped by a net from the security system they installed.
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As usual, Leonard and Penny get into an argument. This time? About psychics.
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Sheldon helps decorate the tree and wants to add the bust of Sir Isaac Newton, which he argues is more Christmasy than Jesus.
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After years of trying to get his mother's affection, Leonard finally gets a hug from Beverly (Christine Baranski). All it took was getting her drunk.
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Bernadette (Melissa Rauch) joins the guys for lunch at work as she begins to bond with Leonard over his work.
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Wolowitz confronts Leonard when he gets jealous over his friend bonding with his girlfriend, Bernadette.
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TBBT Quotes

Penny: Here's a question-- as an alien pretending to be human, are you planning to engage in any post-prom mating rituals with Amy?
Sheldon: There are post-prom mating rituals?
Penny: Not always. Unless your date drives a van with an air mattress, then always.
Sheldon: Well, if it's part of the prom experience, then I'm open to it.
Penny: You're kidding.
Sheldon: I may be an alien, but I have urges.If Amy wants to copulate by firing her eggs into space, well, then, I will happily catch them with the reproductive sac on my upper flermin. I'm not the best at reading facial cues, but I can see that you're a little turned on.

Penny: Hey, Sheldon, did you change your Wi-Fi password again?
Sheldon: Yes, it's "Penny, get your own Wi-Fi." No spaces.