Inside Sheldon's head - The Big Bang Theory

Penny: I'm a Sagittarius, which probably tells you way more than you need to know...
Sheldon:Yes... it tells us that you participate in the mass cultural delusion that the sun's apparent position relative to arbitrarily defined constellations at the time of your birth somehow affects your personality.

Leonard: Shut up Howard! Sheldon, we have to do this.
Sheldon: No we don't. We have to take in nourishment, expel waste, and inhale enough oxygen to keep our cells from dying. Everything else is optional.

Leonard: What was I supposed to say?
Sheldon: You could have told her the truth.
Leonard: That would have hurt her feelings.
Sheldon: Is that a relevant factor?

Sheldon: That is my spot. In an ever-changing world it is a simple point of consistency. If my life were expressed as a function in a four-dimensional Cartesian coordinate system, that spot, at the moment I first sat on it, would be [0,0,0,0].

Sheldon: I'm a physicist. I have a working knowledge of the entire universe and everything it contains.
Penny: Who's Radiohead?
Sheldon: [after twitching for a minute] I have a working knowledge of the important things.

Sheldon: What are you talking about?
Leonard: The cultural paradigm in which people have sex after three dates.
Sheldon: I see, now are we talking about date, the social interaction, or date, the dried fruit?