Visible crew/equipment: When the wolf begins to transform back to evil, as the wolf tries to take the wooden stake out of his heart, he leans forward and you can actually see the human arm behind him. He can't have an animals arm and a human arm at the same time - the arm is of an operator working the animatronic.
Visible crew/equipment: As Charley watches Billy dump a heavy black bag into the Jeep, the shot changes to a first-person view of Jerry walking on the roof getting ready to take flight as a vampire. As he jumps, a crew member and filming equipment are visible. (00:15:15)
Chosen answer: I would assume a "thrall" basically a ghoul that is attached to the vampire. A ghoul in old lore was created when a vampire gave blood to a living person, but did not take their blood first. They were then their daytime slaves, doing errands, finding victims for them, and took care of the vampire's body when the sun was out.
Billy was to Jerry... what Renfield was to Dracula. Slave, daytime watcher.