Penny hugs Leonard after he does his best to comfort her after he ex reveals intimate details about her on his blog.
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Wolowitz teaches Sheldon Mandarin so he can correctly order his Chinese food to make sure he gets tangerine instead of orange chicken. Makes sense to us.
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Leonard and Penny are about to kiss in this still. Leonard finally asked out Penny on a real date after she was hurt by her ex.
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Penny tries to organize a surprise party for Leonard with his friends Sheldon, Howard and Raj.
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Penny makes Sheldon go to a computer store to pick out a gift for Leonard for his birthday but he ends up very distracted.
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Wolowitz uses his peanut allergy to try and distract Leonard long enough for Penny and the gang to set up her surprise party.
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The boys all end up competing for Sheldon's sister, Missy's affection. Raj and Wolowitz even get into a physical fight.
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A picture of Sheldon and his twin sister Missy (Courtney Henggeler) who definitely seems to have gotten the looks of the family.
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The Big Bang Theory Season 1 Quotes

Sheldon: Are you still mad about the sperm bank?
Leonard: No!
Sheldon: Do you want to hear an interesting thing about stairs?
Leonard: Not really.
Sheldon: If the height of a single step is off by as little as two millimeters most people will trip.
Leonard: I don't care—two millimeters?! That doesn't seem right.
Sheldon: No, it's true! I did a series of experiments when I was twelve; my father broke his clavicle.

I saw your pupils dilate when you looked at her, which, unless you're a heroin addict, points to sexual attraction

Leslie [about Leonard's interest in Penny]