[skillya_glowi]

What do you mean by "real"? Real as in, an actual planet probably light-years away which it would be impossible to get to any time soon, or real as in existing here on Earth?

I'm guessing nothing extraordinary would happen to the wildlife. The scrabs and paramites and whatnot wouldn't be treated very different from other big predators - allowed to exist in the wild, occasionally hunted, and perhaps kept in captivity for research purposes and such.
As for the intelligent races, there'd probably be tons of conflict between them and humans. They would be accepted, perhaps, and even respected by some, and yet others would consider them to be beneath themselves. Pretty much the same things different human races used to do/feel about each other. I'm guessing there are many ways human technology could help Oddworld inhabitants; Glukkons could dress themselves and handle everyday stuff with mechanical arms (this makes me wonder; if sligs got robotic legs, why can't Glukkons have robotic arms?) and such, the native species could be provided with resources and space and all that jazz. But there'd always be conflict between the species; same as you see us people starting wars with each other, the Oddworldian races would be pulled into that.