When the popularity of a given serial hits its stride, you can bet that someone down the line will think that making a movie is a good idea and actually has the cash to back it up. If the serial runs long enough and/or if it becomes mainstream fairly early on, then there is a good chance that the movie will be filmed and distributed while installments of the original are still being published. While most of the original readers go to the movie and compliment the visual effects while having reservations about how true it is to the book, there will be a lot of new people that have no idea what’s going on will perceive that this new version is the true one. The weirdness of reader reception of book vs the movie, comic vs cartoon, and even the old school conflict of novel vs play comes into an interesting moment when the actual author is part of that audience.
The most recent example of this can be seen with the Harry Potter books and movies. The first film came out about the same time the fifth book was being written. Now I’ve seen some of the movies and I am planning to work through the books so when I end up reading I’m going to visualize the actors being the characters and not the other way around. The performances of some of the actors are good enough that they end up influencing how the actual characters are being described. JK Rowling in an interview actually said that seeing Alan Rickman being Snape was so impressive that she ended up writing the last books with this vision in mind. I’ve got some friends that insist that Alan Rickman is a real dreamboat and he has an awesome accent so the decision, be it active or subconscious is a pretty obvious one.
In my research I recently read about Charles Dickes going through a similar scenario between Oliver Twist the serial novel and Oliver Twist the theater performance. The novel was barely halfway through when someone got permission to do the stage adaptation, and basically guess what the ending would be. Both in the novel as in the play Fagin was the clear antagonist but at the current installment he wasn’t the full out bad guy. Dickens realized this and had to step up the villainization process in the upcoming episodes. The previous example doesn’t really work in contemporary forms of serial fiction, except maybe with fanworks of something. Imagine if Batman had Two Face with full back story in the movie while Harvey Dent is still pretty much a normal guy.
Speaking of Batman, the best example of one medium interpretation influencing the original can be seen with a narrative strategy known as the canon immigrant. Batman has been going around since pre WWII and shown up in a bucnh of different ways accross the years. One such format and one of my personal favorites was the animated cartoon from the 90s in the WB channel. It had some of the best storylines from the original comics and put stuff in that the movies had also worked on. What made it interesting is that the original content was also very good and made its way into the comics. Amongst these forms of immigration came the character of psychologist Harley Quinn who would become the sidekick and love interest for the Joker or as she calls him “Mister Jay.” The sexy psychopath ended up becoming a fan favorite, showing up in the comics, got her own title, and even has a major role in the most recent Batman Arkham Asylum and Arkham City videogames. Also, fun fact: the voice of harley Quinn in the videogames is done by the same person as Twilight Sparkle of My Little Pony fame. Crazy huh.