Night of the Living Doo, on Cartoon Network
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A mock-Scooby Doo special that aired on Adult Swim in 2001. Or... maybe it was on Cartoon Network proper, before it was ever on Adult Swim (which may have happened in 2002, or something, I really don't remember). Anyway, it was pretty hilarious and had some great guest stars. The Mystery, Inc. gang are on their way to a Halloween movie festival, when they pick up a hitchhiking Gary Coleman. After a little while, their van... um, breaks down... in front of a spooky old castle, so they have to spend the night. The place is run by David Cross, who does his best to deny rumors that there are zombies around. He has an assistant named Shifty (voiced by Mark Hamill), who is obviously (apparently) behind the whole zombie hoax, but the only one who realizes that is Gary. Unfortunately, Gary mysteriously disappears before he can tell anyone what's going on. And um... eventually there's a chase scene, with music by Big Bad Voodoo Daddy. And finally the case is solved, even though none of it makes sense. So um... yeah, it was just really fun. And if you want to see it, you can probably find it on YouTube, or something.