This could be a tale where we slowly watch each family become more and more like the McMillans, We watch as hair slowly turns blonder, people get meaner, till they are all indistinguishable from each other, a mob of McMillans.
Instead, imagine them all in their beds tonight dreaming the same dream, All of them are at a banquet, all the families gathered, Gibson, Ferguson, Meadows, Black and Mishida, and they are all eating, getting along, laughing, the food is fantastic and it takes a second, but eventually someone looks down and recognizes that they aren't eating food, they are eating people, in fact, they are eating the Mcmillans and at once they are horrified, but also it becomes important that they eat more than the others at the table, and the nice family dinner breaks down into a frenzied feast as they all tear at each other to get a piece, the need for more is insatiable.
Then they all wake up in their beds, the dream fades from memory as the strangness of the new reality sets in.
The Gibsons have been given all the physical gifts one might need to be a Mcmillan. They awaken to find themselves beautiful, blond, buxom, and Roger discovers he has three daughters, and Jon discovers she has two sisters, and all of them learn the advantage of being able to turn a head.
The Blacks wake up with the knowledge of what it takes to be a Mcmillan, how to run a company, how to be popular, what to wear when and how all of these new ideas swim in Karyn and her families minds.
The Fergusons wake up with the Vices one might need to do what needs to be done to be a Mcmillan, the ambition, the ruthlessness, the cunning, the willingness to backstab a friend to get ahead.
While the Meadows woke up with all the Virtues one would also need, the charisma, the leadership, the having an eye for the right thing at the right time, and yes even sometimes being generous.
Finally the Mishada's awake to find they now have everything an immigrant family didn't have before, the wealth and established political and social power of the Mcmillans, they went from being the poorest family to on paper the most powerful family over night.
But this can not last, for as the glimmer of that dream fades, and they all eventually go forth to face their days, they all realize this can all go away, for their can only be one true McMillan family after all.