Perspective

I think most people probably know what a prequel and a sequel are but for the sake of clarity the former is a movie set before another, and the latter is a movie set after another.  However I recently discovered there are two other terms which I find interesting, "midquel" and "interquel" which you can probably guess what they mean but again, for the sake of clarity, the former is a movie set during the timeline of another movie, and the latter is a movie set between the timelines of two existing movies.

These two concepts have made me think about timelines in fiction, and the fixed nature of established events.  When it comes to expanding the universe of existing fiction, you are restricted by these events unless you choose to alter the events through a retcon [Retroactive Continuity] or unless you have a plot device in place like Doctor Who which can employ time travel and the impact of it.  That restriction can make it very difficult to expand the universe unless sufficient ambiguity was written into the original script to provide flexibility.

Those are a lot of "unless" caveats however.  There is of course quite literally another angle that you can approach this idea from.  There is an episode of The Simpsons called "Trilogy of Error" which follows three members of the Simspon family, Homer, Lisa, and Bart, in that order, recounting their experience of a given day.  All three stories show the events of the same day from the perspective of the characters which overlaps with the other characters stories but often in ways not realised until later or until all viewpoints have been shown. 

There are also 2 tropes found in writing which play with this concept they are the "P.O.V. Sequel" and the "Perspective Flip" which are closely related yet distinct concepts.  The former details events from an established timeline from the point of view of other characters part of that timeline but detailing events that add to the story but don't tell a separate story - much like the episode of The Simpsons mentioned above, or as TVTropes focuses on, The Lion King 1.5.  The Perspective Flip however actively attempts to change your perspective of the original story, trying to make you hate the protagonist or characters close to them, for example the movie 'Maleficent' retells the story of Sleeping Beauty in such a way that you are intended to gain empathy for her and kindle your indignation for Aurora's father King Stefan.

This whole idea however has left me wondering which movies I would like to see Perspective Flips made from.  I'm a fan of Harry Potter as my twitter suggests, and I have thought about the main story and which characters from it I would have liked to see their point of view shown; I think the only contenders in that regard would be Draco Malfoy and Neville Longbottom.  The former has depth that was never explored and could be used as a device for the author to explore the nature versus nurture debate.  Draco remains a divisive character and some details revealed since by J.K. Rowling haven't been embraced with open arms by all, some readers/viewers still want to hold onto the hardened image of Draco and deafen themselves to anything that contradicts that image.  As for the latter, Neville played a pivotal role throughout the story particularly in the later books/movies which was never explored in great detail.  Those that haven't read the books or explored the cannon of the Harry Potter universe very far will likely be blissfully unaware that Neville was thought to be a "spare" chosen one, some even argued that he is the chosen one and Harry wasn't.  There are a plenitude of fan theories like these which explore these ideas, one thing is clear from the books however, there is a lot of ambiguity that centres around Neville, enough that a story could be written about him and his journey, it might not last seven books or eight movies, but it would be interesting to read and see.