Leonard and Penny act as parents as they go to pick up Sheldon from the comic book store.
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Sheldon comes to visit Penny at work at the Cheesecake Factory to try and convince her to apologize to Leonard to stop the fighting.
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Sheldon shows off his homemade board game, Research Lab where the physics is theoretical but the fun is real! Haha.
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The Big Bang Theory Season 3 Episode 7 Quotes

But if she dumps you, she'll have a new boyfriend by tomorrow morning, and you'll have a new girlfriend when you figure out how to build one.

Wolowitz

Leonard, when that woman moved in three years ago, I told you not to talk to her, and now look, we're going to be late to the movies.

Sheldon