10 Movie Endings Way Darker Than You Realise

Back to the Future's ending sees Marty McFly (Michael J. Fox) ensure that his parents do indeed get together in 1955, thereby securing his own existence.

However, doing so also ends up changing his present of 1985. At the start of the film, his father George (Crispin Glover) is cowardly and timid, his mother Lorraine (Lea Thompson) is a depressed alcoholic, and his siblings have failed to do anything with their lives.

But at the end, their fates have been changed - George is a successful sci-fi author and assertive human being, Lorraine is happy and healthy, and his siblings are doing well for themselves.

Basically, Marty's entire life up to this point has been fundamentally altered, and while the film keeps it ambiguous precisely how Marty's memories will now work, there are basically two options.

Marty either has no memory of his new present and has to awkwardly wing it for the rest of his life, or his altered memories will slowly fade in over time, given that the movie confirms that aspects of the present will slowly update after the past is changed (like Marty's photo of his family).

Either way, it's going to be a tough period of adjustment - having no memory of a childhood the rest of his family vividly remembers, or having to experience his memories being gradually re-shaped over time, which sounds like a sheer nightmare.

One suspects filmmaker Robert Zemeckis would tell fans not to overthink the finer details too much.