6. Christopher Lloyd
When casting the 1996 TV Movie, producer Philip Segal wanted Paul McGann for the role of the Doctor. Fox executives would only allow this if a well-known actor were cast as the Master. Segals first choice was Christopher Lloyd but co-producer Universal was concerned about his fee. Before a deal could be reached, Lloyd became unavailable. Eric Roberts was cast and walked away with a larger fee than Lloyd had asked for. Its difficult to imagine seeing Doc Brown as the Master. After all, he built his time machine for good and the Master uses time travel for evil. But Lloyd has played villains before and had the potential to be a good Master.