Due to some sort of cosmic joke, or the meddling of an undisclosed powerful being, the following families of powerful individuals are transported to and stranded in the MCU, shortly before the start of the Avengers film.
How will their presence affect the MCU and its development? What will be S.H.I.E.L.D.'s (and HYDRA's) reaction to their sudden appearance and the power imbalance they represent? Will they succeed in returning to their respective realities, and will all choose to return?
Lucifer Morningstar (DC) wins a game of poker against The One Above All (Marvel) and the Man of Miracles (Image). The stakes were several races native to their respective spheres of influence (read: universes).
As the winner, Lucifer takes possession of the Eternals, the Inhumans, the mutants, and the Viltrumites. These races, and all who pertain to them, will now be retroactively incorporated into the DC Multiversity's history.
Your challenge, if should choose to accept it, is to develop a believable plot to introduce them into the wider DC Universe, and expand on how their existence affects the history of post-Crisis DC as we know it.
Due to a technical mishsp, these families and individuals are brought over across their respective dimensional thresholds and into the mainstream Marvel Earth, Earth-616.
They are met with the violent mistrust and quasi-homicidal paranoia which is par for the course for the "heroic" teams, individuals, and paramilitary governmental organizations of the "Xenophobes'R'Us" Earth, aka Marvel Earth 616.
How far do they go and how many so-called heroes dothfy go through before common sense prevails? At what point do they meet their match? Which individual or team is beyond their collective abilities?
Starting point for our cross-dimensional visitors is the International World Fair grounds in New York.
BFR is allowed.
Victory is by KO of all opposing side's members.
Cartoon physics are in play for all three anthropomorphic superpowered animals.