6. Crispin Glover: Then
In the original BTTF, Glover played two versions of the same character. He played George McFly, Marty’s dad, both the older version in 1985 and the younger one in 1955. Glover was already in the acting game before BTTF. He’d even been in two episodes of the series, “Family Ties,” with his costar Michael J. Fox, where he played a character named Doug. Sadly, it wasn’t all paradise for Glover on the set of BTTF. He and director Robert Zemeckis butted heads on the ending, an ending which Zemeckis ultimately did change. But, Glover paid a price for his pushback. When they cast the sequel, Zemeckis left Glover off the cast list.