Johnny Galecki contemplates a difficult question here. The actor was a popular presence at Comic-Con.
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Johnny Galecki may play a nerd on the show Two and a Half Men, but the actor is anything but.
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TBBT Quotes

Sheldon: Why do people cry at weddings?
Mary: They're practicing for what's coming later.

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