Goofs

When the minutemen first confront the ghouls they are shooting at them across a stone bridge, it then becomes a wooden one.

In the opening scene, Mr. Archibald is wearing modern-style glasses, which then never reappear for the rest of the movie.

When the militiaman goes to alert the minister about Boo, he's carrying a long musket. When he returns with the minister, he's now carrying a pistol.

There is clearly writing on the back of the poster Barnaby composes advertising Abigaile's voice. Later, Number Two can be seen reading Finnuius and Abigaile's sentences from the back of that same paper, despite the fact that when Barnaby was writing it, they hadn't even been discovered yet.

Barnaby's henchman Sam can be seen burning Abigaile's mother at the stake (his hood falls away briefly) despite the fact it was several years before he and Barnaby arrive in town. He can later be seen in the crowd taunting Abigaile after her arrest, despite the fact that it occurs after he's been killed.

Terrance has no visible wounds, despite being shot.

Modern locks and deadbolts on the doors in the wench's room and Matilda's house.

A modern light switch can be seen on the wall in the town wench's room.

During the scene in the parlor of Matilda Grissom's house, a modern-style "PRIVATE" placard can be seen on the door.

A modern cast-iron historical plaque can be seen on the wall outside the mill where Matilda's and Boo's body are.

"Row, Row, Row Your Boat" with the modern tune and lyrics was not published until 1881, more than 100 years after the apparent time period in which the film takes place.

Abigaile misspells her own name as "Abigal" on the chalkboard she passes to Finnius in the schoolroom flashback.

[Possibly intentional by the filmmakers] The characters in the film continually (incorrectly) refer to the "ghouls" when they are actually "zombies". Technically, a "ghoul" is an undead person or demon who eats the corpses of dead people, while a "zombie" is a formerly deceased person who returns to life, usually reanimated through magic, to eat the flesh the living. This is intentional on the part of the filmmakers, because in the late 1700s and early 1800s when the film takes place, the word "zombie" had not yet made it into common English vernacular.

When the militia man catches Barnaby in bed with his wife. While he's pointing at Barnaby, you can clearly see a modern wrist watch. Those haven't been invented yet.