Character mistake: In the scene where Sophia confronts Celie in the cornfield, she starts by saying, "You told Harpo to beat me". Later she tells Celie, "If you want a dead son-in-law Miss Celie, you keep on advising him like you do". Harpo is actually Celie's stepson, NOT her son-in-law.
Character mistake: When Schaeffer, McFee, and Fergie walk down the dusty road to Amish village, Western gunslinger style, they make a silly mistake no cop would make - they assume that Amish villages are unarmed and undefended. No so. The Amish have no prohibition on guns and almost every house would have at least one hunting rifle or shotgun. The three bad guys are risking being shot to bits before they get halfway down that hill; they don't even make an attempt at concealment. (Wouldn't they also at least think John - a police officer - would still have his gun or might have got hold of a firearm from the Amish?)
Character mistake: When the front door of the old F-unit is refusing to open the guys put their shoulder to it. The door they are trying to bash outward actually swings into the area where they are standing. If they really wanted to go out that door they should have unlatched it and pulled.
Character mistake: When Burt, Ernie and Spider go into the hall after questioning the zombie Burt says his own name instead of Ernie or Spider.
Character mistake: Morgan Hiller's father is named Stewart (according to the story as well as credits). But in one scene when Morgan and his parents are having dinner, Mrs. Hiller calls him (her husband) "David" one time (instead of Stewart).