3. Neil Diamond As Superman

Despite the grand history of musical stars taking on screen roles, nobody in their right mind would ever have consciously considered casting odd-haired, odd-voiced singer Neil Diamond as Superman. Or so you'd have thought. Somewhat unthinkably, the crooner was under consideration by the Salkinds when they took on the Herculean task of bringing Superman to the big screen. He supposedly lobbied hard for the role, despite how deeply unsuitable his hair was for either Supes or Clark Kent, and incredibly wasn't as immediately dismissed as you might have suspected. But then this is the same team who strongly considered Chris Walken for the same part. While baffling on its own, that casting (or any alternative casting for Richard Donner's Superman) would have robbed the world of the chance to see Christopher Reeve offer a definitive take on both sides of the character. On the other hand, the idea of seeing Superman the musical starring Superman would be too much like something from The Producers to possibly pass up.