In the movie when Michael is looking for his sister, he looks in some files, and finds a file for Laurie Strode. But everyone knows that after the second Halloween, Laurie entered the witness protection agency and lived as Keri Tate. If she was really living as Keri Tate, there would be no files for Laurie Strode. It would have been as if Laurie never existed. A HUGE mistake!