The biggest grossing movie of all time is hardly remembered, referenced, or thought about. It's cultural impact is less than Austin Powers – a "Shagadelic, Baby!" would be understood by many people, but anything but the most generic reference to Avatar wouldn't, despite Avatar being a more recent movie.
I remember hearing news stories about people losing their minds, watching the movie over and over, wanting to be one of the Na'vi (the big blue tribal monkeys). So you would imagine it might have a more intense fanbase than normal, even if the general public has moved on. But looking at fanfiction.net's rankings of contributed works belonging to movie fandoms, Avatar ranks embarrassingly low.
Not just below Camp Rock and Tangled (movies you may not have ever heard of ), but below Sky High, a Disney superhero movie all but forgotten these days due to its seeming support for strict social hierarchies and possibly even eugenics – that the movie portrays someone as a hippie for calling the system 'fascist' makes me worry that dark moral of the story was intentional. Bizarre, and best left to the scrap heap of cultural history – and yet, it is not yet as forgotten as Avatar.
This is all to beg the obvious question: do all movies routinely cause some small percentage of people to become obsessed, watching the same movie over and over again, and wishing to be one of the characters? If a movie as nothingburger as Avatar inspired that, maybe this happens all the time (but presumably at lower numbers).
I admit this is a terrifying thing to think about, but if it always happens a little, it's the perfect news story to run for the biggest box office hit of all time. It's about the movie, and about it being popular, but doesn't spoil anything, and doesn't talk about movie executives (who are boring at best). That they even knew to look for a story like this concerns me, but I have no specific information about the obsessives a movie might inspire.
I hope they get past it, is all I can think, and settle into a more normal and psychologically healthy fandom. The people who become obsessed with Avatar or any other movie shouldn't have to live in a universe they don't want and (obviously) this means their preferences have to change. That's a tricky thing. Very recently I met a young woman who's favorite movie is still Twilight – and not just, on reflection, but she brought it up, a couple times. Imagine all those other people, whose obsession is less well known, so they feel they could never bring it up.
The more I think about this the more I think this impulse is probably older than modern motion pictures. I'm a bit sad that we create so many good stories that people with this tendency are no longer sucked into obsession with the Bible – say what you will about the text, but we know for a fact it's possible to live a happy and healthy life while obsessed with it beyond normal standards. And as much as the Christian Moms Opposing Witchcraft were worried, it seems Harry Potter (by far the biggest fandom on fanfiction.net) is also reasonably healthy, including, for instance, noted businessman and author Hank Green, who used to run a prominent (this existed?) Potter-rock band. Perhaps, given enough time, everything can be healthy? I suspect it's just that only the healthy ones have cultural staying power.