I came across this video by Chevrolet, The Mill and Unreal Engine, who have collaborated to create a real-time customisable short film. It crosses into an augmented reality where the viewer can choose what they want to see. They are able to choose the type of car, the colour, the backgrounds, the style.
The possibilities that this sort of content opens up is crazy. Soon directors will be able to control every little aspect of their film, without time penalties, therefore not impacting too much on the overall budget.
At the moment, the set-up involved for this sort of content would far outweigh any benefit of having it. However, in the future maybe we will all be watching entire films with characters looking exactly how we choose!