Doc doesn't know who Biff is, Doc is insistant on Marty not seeing HIS former self, they have different names, Marty isn't a scientist, Doc's shit on a Hoverboard and Marty actually dies in the alternate ending to BTTF 3, which would kill Doc but it doesn't.
(, Thu 21 May 2009, 5:25, archived)
Marty McFly is obviously Doc Brown's dog Einstein from the future.
(, Thu 21 May 2009, 8:30, archived)