Did you read pick-a-path stories when you were a kid? These are the books where you can decide what the character should do next, and turn to a different page for each possible action?
Now we have pick-a-path movies. This article from the New Scientist describes a new type of headset that literally reads your mind and changes what happens in the movie according to what you want to happen next. If you want the character to fall in love and live happily ever after, they will. If you want the romance to end (far more interesting, I say!), it will.
But should movies only do what you want them to? And what happens if two people want to watch the same film?!