When the brothers arrive in town the first night, there's a crescent moon in the sky. However, the second night when the werewolf strikes, the moon is full. The moon doesn't change phases that fast from crescent to full in a single night.
When Dean says this line after taking the ribbon out of his pocket to show Sam in the bar after his fight with Dracula: "This, I uh, pulled it off during the fight" his lips don't move, and the volume is different from the rest of his line, you can clearly tell this line was added in post as a voiceover.
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