When Slip and Sach (locked in the closet) saw through the wall, there is only a horizontal cut. The next shot shows the other side of the wall (inside the gorilla's cage); there is a vertical cut at a 90-degree angle to the horizontal cut (showing that time must have passed). They eventually cut a big hole in the wall. Later on, when Dr. Gravesend puts the gorilla back in the cage, the back wall shows no evidence of the hole Slip cut into the side wall a few minutes earlier, and now blocked from the camera by a curtain.
Dr. Gravesend shoots Slip's hat off with a flintlock pistol. Afterward he keeps the pistol aimed at Slip and Sach. Everyone acts like the gun is still loaded, but it's a single-shot pistol and he hasn't reloaded it.
At 1:02:03, Slip, Butch and Chuck try to break down a door. As they ram a podium into it, the entire wall shakes, revealing it as a stage set wall.
Francine Gravesend is called a vampire(ss), but she's pretty much just a femme fatale. She never drinks anyone's blood (though talks about it), and she's up and about the next morning after the sun rises. She's more a woman with a vampire complex than a member of the undead.