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

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

A neutron walks into a bar and asks, "How much for a drink?" The bartender says, "For you? No charge."

Sheldon