By rights, if the real Elvis actually existed within each self-contained movie universe, then his alter egos wouldn't have been able to go anywhere without being mistaken for him and mobbed on a constant basis. His alter egos' protestations that they weren't actually Elvis would also have fallen on deaf ears - what with all those "let's stop the movie to perform a song" moments!
Perhaps Elvis should have done a semi-autobiographical movie in which he tried to evade fans by disguising himself as another person. It wouldn't have been any more ridiculous than half the other stuff he did. Of course, Elvis recently redeemed himself with the independent production, "Bubba Ho Tep". Quite possibly his most complex and affecting performance... Oh, wait.