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

Two tea bags in one cup? You're not at a rave.

Sheldon

Raj: Okay, here's another one: if a zombie bites a vampire, and the vampire bites a human, does the human become a vampire or a zombie? Or, a zompire?