Leonard Hofstadter

Ostensibly the main character of The Big Bang Theory, Leonard is the most normal of the guys by never having any outlandish quirks and generally operates as the Only Sane Man. He (and his friends) work at Cal Tech, his field being in Experimental Physics. He has lived with Sheldon since late 2002 and is his best friend, though Sheldon's quirks annoy him to no end. He instantly gained a crush on Penny when she moved into the apartment across the hall and much of the show is about how they both change from interacting with each other.