Ask yourself seriously Would you believe Val Kilmer if he told you he was a quarter Sioux? It's possible. It was probably more plausible in 1992, when he starred in the crime thriller Thunderheart, and his face was less bound to the blockbuster roles he's known for.
www.theparallaxreview.com/on_cable/thunderheart.html
www.theparallaxreview.com/on_cable/thunderheart.html