Crossover episodes aren't anything new - they've been around for years, and some of the most unlikely TV shows have done it.
For example, did you know there's an episode of Murder She Wrote where Magnum PI turns up? Anyway, crossover episodes have been enjoying something of a renaissance of late - which is probably why long-running horror series Supernatural is now crossing over with also long-running horror series Scooby-Doo.
That's right, folks - the Winchesters are going to hang out with Scooby-Doo and the Mystery Machine. The episode will air on March 29th and the first bit of footage has made its way online for everyone to be baffled over.