In one Fringe episode that takes place in the alternate universe, Eric Stoltz is Marty McFly in “Back to the Future”. This made me curious and I checked out Wikipedia: In our universe, they actually shot five weeks with him in that role before replacing him with Michael J. Fox. It feels like the right decision and I don’t think it is Michael J Fox’s acting, but rather his personality that make him such a great fit. Now you can actually see a little bit of footage [source: Gruber] from those first five weeks.