Linda Blair

The Exorcist (1973)
Role: Regan MacNeil

Then: Blair was 13-years-old and an unknown when she was cast as possessed little girl Regan MacNeil in The Exorcist. But she quickly gained fame (and an Oscar nomination) for her devilish performance.
Now: Blair appears as herself on reality shows sometimes, but has basically stopped acting. She devotes much of her time to the Linda Blair Worldheart Foundation which fights against animal cruelty.