Plot hole: The first time David werewolfizes, he's reading a book in the brightly lit apartment. Exterior shots of the full moon show it's nighttime out, so the lights inside the apartment must be on. But when Dr. Hirsch calls to check on him, the shot is of the phone ringing, unanswered, in the completely darkened apartment. That's considerate, David. Even as a werewolf, he must have run around turning lights off before going on his rampage.