Do not make the same mistake we made: do not start with this episode.
I've always kind of liked Scooby-Doo as a concept and as an early attempt at animated horror/comedy. But I've never actually seen an approach that worked. The originals had some cool designs on some of the monsters, but the stories were never interesting.
Well, this is where that changes.
Scooby-Doo! Mystery Incorporated updates the concept and characters in a way that remains true to the show's original concept and history, while simultaneously offering extremely intelligent writing, complex character and relationship development, as well as multi-season plot arcs with satisfying payoffs along with way. I don't just mean "satisfying for a cartoon," either: this is the kind of in-depth, multi-dimensional story telling that's rare on live-action TV.
We, of course, stumbled across it because of the Christmas episode. Only it's not really a Christmas episode, at all. The hook is that Krampus is attacking misbehaving children of Crystal Cove, and the gang are trying to trap him.
Yes, Krampus, the demon who drags away bad children to torture them is around. It's summer, so his presence is a little odd (they do acknowledge that, by the way). The show did a good job depicting him, tongue and all, and he's a little scary. Nowhere near as scary as the abandoned doll factory they chase him into at the end, though: that place is the goddamn stuff of nightmares.
In the end, it turns out Krampus was a robot. It's not immediately clear who's controlling him or why. When they reveal who's really behind the mask, the explanation is completely ludicrous (intentionally so: this trend dates back to the 60's, and the writers of Mystery Incorporated are very conscious of what they're doing). It's also awesome.
That said, everything having to do with Krampus is really more a B-plot. The episode is far more focused on a massively complex story line that's been in development since the first episode.
This is a lot of fun. On top of that, the comedy was witty and entertaining, particularly in the resolution. The horror elements are even decent. But I can't stress enough how important it is not to start with this. This show is absolutely amazing. Lindsay and I immediately jumped back to the first episode after watching this one, and we're working our way through the series.
I'm dropping a "highly recommended" label onto this episode, but - as is often the case for TV shows - it applies to the series as a whole. This is the Scooby Doo you probably never realized you always wanted. But hey, uncovering secrets is what the gang does.