Who Framed Roger Rabbit had toons and people living together. Now my question is this: when did toons and people start living in the living universe or did humans start living in the toon universe instead? I would like to know if there’s a in-universe answer if possible.
In the film's source novel (Who Censored Roger Rabbit?) there's every indication that toons have been around as long as regular humans. There's some speculation that toons and humans are both offshoots of the same evolutionary tree.
Had the DeGreasy boys been discovered frozen beneath some Arctic tundra, a good case would probably have been made for their being the long-sought missing link between humans and Toons.
"Not particularly. No more so than I imagine it might be for you to throw one of your fingernail clippings into a trash can. Oh, I'm sure there are primitive tribes in Africa or somewhere who treat their doppelgangers as mystic offshoots of their soul, but we modern, civilized Toons regard our doppelgangers as animated mannequins, nothing more."
Toons appear to be well established in both pre-colonial America and in large numbers in Indo-China.
His great-great-great had crossed over from the old country on board the Mayflower and had been the guy who arranged to have the nation's first Thanksgiving dinner catered by the Toons the colonists found living here. For this Jess's ancestor got his name in the history books. Another of Jess's relatives had imported thousands of Toons from China to build the nation's first transcontinental railroad. They became known as the Yellow Kids and won that relative a spot in the history books, too.
As best I can tell paging through the material online, there is no indication the Toons haven't always been there, side by side with humanity, as second class citizens. This jibes with the book it was based on, Who Censored Roger Rabbit?.
I believe in the book there is a single sentence about Columbus encountering toons for the first time when he landed in North America.
That doesn't really explain much but the story just runs with it.