Jennifer Parker/George McFly

Both Marty McFly’s girlfriend and his dad are played by different actors in the sequels than they were in the original. Sadly, instead of adding and awesome, hard sci-fi subplot explaining that through time travel, Robert Zemeckis simply re-shot Claudia Wells’ scene from the end of the first one with Elisabeth Shue and gave Jeffrey Weissman prosthetics to make him look more like Crispin Glover. A very nerdy opportunity missed.