All it takes is one role to catapult an unknown actor into the stratosphere of superstardom. No matter where they started, every A-Lister became a household name because of a single part in a single movie that made the world stand up and take notice. Yet for every one of these roles, there are numerous stories about the actors that almost booked them. However, for one reason or another, they worked on other projects while someone else turned in a performance for the ages. While there are far too many to detail in full, here are a few of the more amazing and mind-boggling of them.