Actors can be divas, but sometimes actors "acting out" can actually work in a film's favor. In a few cases, actors who altered their parts--often to the chagrin of producers--actually created unforgettable characters. Some iconic characters turned out quite differently from what was originally written, but some movies earned awards and acclaim they very well might not have garnered without the creative insight of the talent. As most filmmakers will say, the movie process has to be somewhat flexible because there are hundreds of issues that can arise during the extensive process of creating a film.
Actors who changed their characters for the better include big names like Johnny Depp and Al Pacino: their deviant decisions are how iconic characters were born. Here's a list of famous roles that could have looked much different without the actors' vision to guide them.