What Causes Eyes to be Blue and Brown?

David Bowie has one brown eye and one blue eye as a result of a friend thinking it would be funny to see what happened when you mixed an eye with a stick. Aside from accidents, one blue eye and one brown eye is a genetic anomaly that is very rare and should be treasured if it ever happens. If one of your eyes suddenly changes from brown to blue however, you should see your eye doctor. Either that, or you are in a bad horror movie.