Because you like Kim Kelly in Freaks and Geeks
Edmund Pevensie isn't a bad person, but he did sell his siblings out for a tin of Turkish Delight. See them in The Chronicles of Narnia.
Bad-ass Rayne has sworn her life to finding and destroying her vampire dad, Kagan, and killing as many other vampires as she can in the bargain. See them in BloodRayne .
Prim and proper Allie Hamilton was raised to follow the rules. But she's got a fiery rebellious side too. See them in The Notebook.
In the simplest terms, in the most convenient definitions, people consider Brian a nerd. But he's more than that. See them in The Breakfast Club.
Kathryn Merteuil may be a vain sociopath, but you won't be able to look away. See them in Cruel Intentions.
Maurice Moss is a dedicated IT guy who even talks like a computer. See them in The IT Crowd.
Cyclops shoots lasers out of his eyes, destroying anything in his line of sight. See them in X-Men Series.
Elaine Benes is a tough New Yorker who can hang with the guys, and date the ones who are "sponge-worthy." See them in Seinfeld.
Just call Jeff Lebowski The Dude. Or His Dudeness, Duder, or El Duderino if you're not into that whole brevity thing. See them in The Big Lebowski.