Tfp x Pacific Rim.
They've been on earth a while, then suddenly a giant kaiju pops up and they learn humans have giant robots as big as Plexs (the bots that turn into cities) The biggest bots in the series are only around 30-40ft, jaegers usually reach past 300ft. A jaeger could stomp Optimus and Megatron into the ground and never notice it. And they're only piloted by two humans, mentally in sync and battle hardened, willing to kill anything that threatens their planet. The horrifying realization that humans could wipe them out if they really wanted to.
Or maybe it could be post TFP, and they all decide to come back to earth to visit/see the kids, and are immediately held at jaeger gunpoint, or witness a kaiju flatten a city.
This immediately came to mind.
I don't know what would be more humiliating for a Cybertronian. Getting your ass kicked by Pacific Rim's Jaeger or Kaiju No 8's Defense Force with their exo suits. I guess how close the human is determines that.
Going off canon here with both factions just arriving on Earth instead of being present for three years or returning. This is because Pacific Rim's PPDC absolutely slam down any attempts for the bots to continue their war. Dealing with Kaiju made by hostile aliens is already a handful so extraterrestrial beings who can't end a millennium long feud turned 'spat' is unacceptable.
Both factions get captured as the Decepticons are first. Radars caught the Nemesis appearing in Earth's atmosphere and two Jaegers immediately intercepted the ship. Buckethead is still pissed about it as EMPs were utilized for incapacitation once their machine like nature been seen.
The Autobots took longer to find since they immediately went into hiding. Raf, Miko and Jack are responsible for their respective bot guardian's capture. A Kaiju attack had occurred with the kids being unable to evacuate to safety.
Bumblebee, Arcee, and Bulkhead risked their cover to protect them from the monster. The kids were watched over by the bots as their families hadn't been located yet. Original plan was to return the Jasper Trio home and disappear once more.
Something that doesn't happen as another Kaiju attack near their base led to the PPDC finding the Autobots. Jack, Miko and Raf were able to plea for them to not hurt the group. Both the Autobots alongside the kids get taken into custody afterwards.
Or how the war came to a humorous yet humiliating end as both factions were forced to make peace with each other.











