Because you like Gregor Samsa in The Metamorphosis
John Yossarian is trapped in irony as he must be insane to leave the war but if he does try to leave, he'll be deemed sane and will be forced to stay, See them in Catch-22.
Marv is a brutish but principled thug who'd be right at home on an ancient battlefield. See them in Sin City.
Riggan Thomson is a washed-up movie star running from his inner demons. Alas those inner demons look just like the superhero he used to play. See them in Birdman.
A champion of chivalry, Don Quixote is dutifully bringing good to the world—even when others think he's out of his mind. See them in Don Quixote.
Victor Frankenstein can create life, so he's pretty awesome if he says so himself. See them in Frankenstein.
Sometimes being a supportive girlfriend like Ophelia doesn't work out too well. See them in Hamlet.
Jean-Baptiste Grenouille may have a phenomenal sense of smell, but he has a weak sense of morality. See them in Perfume: The Story of a Murderer.
Marge Gunderson embodies the very best of the American Midwest. She's kind, friendly, and fiercely honest. See them in Fargo.
Combining an innocent face with an insatiable bloodlust, Eli recruits friends to join the vampire way of life. See them in Let the Right One In.
Roger Kint is a nervous, weak, ham-handed criminal. We think. See them in The Usual Suspects.
Macbeth was probably named "Most Likely to Kill His Rivals" in his senior yearbook. See them in Macbeth.
Frederick Frankenstein is an eccentric (O.K., maybe a little insane) professor who is excited to be delving into his family's past. See them in Young Frankenstein.