Dr. Sheldon Cooper is Leonard's best friend, roommate, and co-worker at Calech.  Sheldon is the smarter of the two with an IQ of 187, but is definitely the more socially awkward of two.  He has a ridiculous ego, is extremely stubborn, but the group seems to put up with him.

Sheldon Cooper 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

TBBT Quotes

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

Sheldon

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