I haven't shared this here yet??

I had this idea AGES AGO oh man
Student Movie! AU: where the entirety of Rainbow Rocks is a collaborative project between some of the music groups in Canterlot High (the Rainbooms, the Dazzlings and Trixie And The Illusions) which turns out startlingly good considering their budget. Note: only Rainbow Rocks affected, the other three happen as they happen.
-when they all start working on the script the Dazzlings volunteer to be the villains because listen our group is themed around SIRENS do you KNOW how much villain potential mind-control mermaids have?
-Sunset Shimmer is like "fun fact Sirens actually exist in equestria" and then "hey I just remembered something mb we can do a thing"
-contacting Twilight Sparkle because maybe they're actually onto something with the equestrian sirens thing and eventually all of their ideas morph into Rainbow Rocks
-At some point Twilight figures out the portal thing so they actually get to film ON LOCATION in Twilight's castle and with her pony friends
-(Rarity practically swoons when she realises she's being invited to a CASTLE by a PRINCESS, and can't hold back her excitement when the Rarity native to equestria invites her to her boutique. ("YOU DESIGNED FOR A ROYAL WEDDING?" "Oooh this fabric is gorgeous! Would you ever consider selling me some?"))
-(Human Rainbow starts tying her hair up in Equestria so she can be told apart from Pony Rainbow. Pony Rainbow also teaching her how to fly properly so they can race.)
-The Rarities and Twilight working together on making the storybook the Sirens show up in because the existing legend is great to base it off of but it wouldn't explain how they got to the human world, bc in this AU the equestrian sirens weren't banished (ofc)
-at first Trixie isn't involved and it's just the Dazzlings and Rainbooms wanting to make a thing but somehow she gets involved anyway
-the starting budget for the film isn't very much but when the portal to equestria opens it goes WAY UP because Twilight donates Bits and as it turns out (after Sunset Shimmer points it out and it's tested) they're made of ACTUAL REAL GOLD, and the gems Spike gave them are somehow? worse???
-("This is a diamond. This is a diamond the size of my fist. I don't think we can sell this, we'd get in trouble for scamming. Hey Rarity want to make yourself some 'costume' jewellery?")
-(at some point the Equestrian government notifies the US government of their existence and the situation because at this rate these kids are going to get in trouble for this. Somehow a bunch of high school students become legal, and the only, suppliers of equestrian gold to the US government.)
-the rainbooms literally buy professional movie filming cameras and software for editing and special effects and other misc equipment because not only do they have a bunch of money from selling bits but they also have a SALARY now and it's a lot
-Principal Celestia and Vice Principal Luna are a little bit surprised when a group of their students ask if it's okay if they film at the school because normally if some students want to do a home movie they don't bother asking permission but then they're shown the cameras and the storyboards and concept art, not to mention the endorsement agreement from the Equestrian Government which they didn't even register was a THING before then, but this is clearly a much more serious endeavor than most student movies so yes we'll get you some permits, just don't let this interfere with lessons and yes that includes yours.
-they hold auditions at the school for background and supporting characters and pretty much everyone is into it, especially once it's mentioned that Princess Twilight will be visiting again to play in it.
-In fact, everyone pretty much everyone auditions to play someone. Flash Sentry gets the part of... himself, and is elated by this fact, because he's not actually very good at acting. He starts to practice in private so he doesn't mess it up because he's one of the few supporting characters who has speaking roles. (when shooting rolls around he has to reshoot the scene where he gets mad at Twilight multiple times because he keeps apologising about it before the scene is over)
-shooting is nearly finished when the friendship games happen, which goes pretty much exactly how it did in the movie. Scitwi is added to the movie crew as a digital effects artist and even gets her own teaser clip at the end of the movie, and agrees to get involved if a sequel happens too (which everyone silently agrees will be a recreation of the friendship games event)
-whenever they're not busy with their other duties, Rarity, Pinkie and their counterparts start working on marketing. "Rainbow Rocks" social media accounts with things like posters, teasers and even on-set photos from between scenes are made, and the hype for the movie slowly grows. While the writers and directors are originally kept anonymous, at some point the movie's popularity BLOWS UP to massive amounts when people find out that this musical modern fantasy epic blockbuster is being made nearly entirely by teenagers and movie critics are already praising it and calling everyone on the crew a prodigy even before the official release date is revealed.
-somehow these kids get a proper theatre premiere and the tickets are sold out in a day, along with the tickets for every showing for a month, because while Rainbow Rocks might be considered "eh" here where it's an animated movie about a kid's show, in the world it's set in it would be more along the lines of epic fantasy blockbuster (like Harry Potter but w/ more girl power and not based off a book so no "adaption fail" problems)
-lots of people are stunned by the scenes filmed in equestria because THEY LOOK SO REALISTIC HOW THE FUCK? IS THIS EVEN CG (no, no it isn't. In fact, most of the magic in the movie isn't CG either, the only bits that are are most of the stuff from the final fight)
-there's a slightly less big premiere for the equestrian release because the movie industry there isn't as big but it's still very popular and even the princesses attend it
-the mane six visit the human world to attend the premiere and lots of people are very confused to see slightly-older-looking-and-differently-dressed doubles of the leads
-(they're even more shocked by Spike. Twilight managed to do something with the portal to let Spike through as a dragon, just for the premiere, and he is ELATED but everyone at the party who didn't work on the movie has a mental bluescreen and has to reboot)