How it hasn't happened yet, I'm unaware. Buffy the Vampire Slayer/Jennifer's Body crossover. There are spoilers for the end of the film in this challenge.

Post-Season Seven of BtVS (AU is fine, too, as long as there's a Watcher-type council which the Scoobies are a part of, and there are many Slayers). Post-Film for Jennifer's Body (including possible end shift).

While the Scoobies/New Watchers wouldn't normally investigate a place with such an obvious name as "Devil's Kettle" (Hello, Sunnydale!), mystical energy emanating from the town causes some alarm. Especially when if b...