Continuity mistake: At the end, while Billy chases Kelli, Kelli knocks over a cart of surgery supplies, spilling the material forward. However, a few shots later, Billy is shown picking a scalpel up from the small tin pale, which slid ahead of Kelli. So how could Billy have picked up the scalpel if he was behind Kelli?
Black Christmas (2006)
Ending / spoiler
Directed by: Glen Morgan
Starring: Mary Elizabeth Winstead, Michelle Trachtenberg, Lacey Chabert, Katie Cassidy
Most of the murders commited in the house were not by Billy but his half-sister/daughter Agnes, hence her M.O. of duct taping her victims heads, then gouging out their eyes (which is what Billy did to her back when she was eight). By the end of the night only Kelli is still alive, Kyle and Leigh having joined the other deceased house occupants. Billy dies of his burns as his home goes up in flames while, Agnes is electrocuted when the paddles on a defibrillator on max power is used on her head.
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More mistakes in Black Christmas
Dana Mathis: Are you high? It's freezing out there.
Trivia: The sorority mom, Andrea Martin, is also one of the girls in the original "Black Christmas". Her name in the original was Phyllis.
Question: Why would Agnes join Billy in his killing spree? She was a victim of him, losing an eye and her parents. She could've joined the sorority girls in stopping him.
Answer: Maybe like him she's also mentally ill, getting it from their mother. Maybe she feels doing this will bring them together.
Answer: Because Agnes is in love with her fatherbrother, and besides, they were invading her home, from her perspective.
ChristmasJonesfan