3. Charlie Sheen and Sean Young
This goes back way before his Two and a Half Men or his Tiger Blood days. Back in 1987 when young Charlie Sheen was filming Wall Street, Sean Young was apparently so sure that she should have been playing the role that Darryl Hannah got that she started a campaign about it. Not surprisingly, Charlie got more than a little bit fed up of this behavior and taped a sign on her back which she wore for hours before anybody had the heart to tell her. What did the sign say? Use your imagination.