Really quick Undertale X TFA thought:
Another fallen human oc, or simply the Frisk of their world, or maybe the descendant of one of the Monsters or Frisk.
Frisk emerged with the Monsters from a Pacifist Route.
Either 50 years passes by for the next generation to appear, or OC/Frisk/their Monster ends up getting a job in Detroit sometime after being freed from the Underground.
They may also take up a side hobby of posting videos of them singing original lyrics to their friends themes. I took inspiration from Ori Eta, Jenny [xUnreachablee] on YouTube.
So, they end up meeting the Autobots, seeing the Decepticons in action.
And as per the stuff they have listened to/witnessed through the spread of information through history records, they question things.
Everything.
How the war started, why the war started, how did the war end previously, what circumstances lead to the new Decepticon uprising aim to be conquering Cybertron and possibly the galaxy.
Optimus shows them the Cybertron War History Essays:
"...Roses are red, Flowey is prickly. That is propaganda, and we need to end this quickly."
They begin to hold protests with their online followers/fans. They also spread information via their connection with several other humans and monsters.
Guys, imagine Mettaton trying to be political-
And you know the awesome theme song with the godly guitar shreds?
Protest song. Boom.
Call it 'More then Meets the Eye,' slow the pace, make some emotional lyrics, and;
We Supreme!
I have this whole scene layed out too:
Driving up to a big stage set up during the previous night in one of the Bots' alt modes. Sari is coming with them, wearing the specially designed mask she was gifted to wear in a live performance for Human-Monster Peace Day (sung a bunch of storytelling songs, mainly based from Ori Eta's covers. She was included with two other Monsters/another human and another monster).
Sari asks what they're going to do as they get out and they answer her with, "Peacemaking." As they put on their signature Music Sensation Mask and smirk like a melomaniac as Sari and the Bots' jaws drop (watch out for Bulk's, may be too unhinged).
They do the protest song, Sari trying to copy some dance moves and helping play a few notes on her xylophone in tune with the ones at 'Trans-form-ers, more then meets the eye!'
A humongous crowd, practically the whole city that they've reached out to is whooping and cheering, showing their support.
The entire thing is being streamed throughout the galaxy using Teletraan-1.
The Decepticons on Earth certainly won't be missing it.
Soon there is exposition. Several links to sources and personal interviews pop up on a display screen behind them for reference. Information about the war, the wrongdoings, corruption, and how they can try to amend these failures.
One thing leads to another, and eventually Sari and then join the crowd on equal footing.
They hold hands, encouraging everyone to grab each other's hand as they make a call to action.
And then they take of their mask, revealing their identity.
The other citizens hiding their faces remove them as well.
Several human SOULs begin floating out chests, rising higher to complete a giant show of a multicoloured heart above them.
All that's left now, is to see the rest of the galaxy's reactions.
