From MoviePilot.com: Back to the Future Theory: Marty Made Jennifer Look Different by Jonathan Sim
I’ve only created one Back to the Future theory before (click here to read it). But here’s a theory that I think is VERY plausible and it surrounds the recasting of the role of Jennifer Parker in Back to the Future II and III.
In the first Back to the Future movie, Jennifer was portrayed by Claudia Wells. In the next two, she was portrayed by Elisabeth Shue.
Read the rest: http://moviepilot.com/posts/3751135