I'm just remembering all the Scooby Doo rip-offs. I guess The Funky Phantom would have been definitely off limits; he was literally a dead guy with a dead cat! (He was also a patriot during the Revolutionary War, so I guess there was that too).
Goober and the Ghostchasers: more often than not, there turned out to be a real ghost somewhere in the story, even if there was some scam being perpetrated.
Clue Club: back to Scooby Doo mechanics. The supernatural happenings and monsters were cover-ups for some local scam. The only problem I see is 13 years old Dottie is the smartest kid in the room, and often "accidentally" turns up on the scene when she's been told not to by the older kids.
Captain Caveman: probably because of the caveman factor, but I was always more concerned by the relationship of a basically naked old man with three teenaged girls. There was definitely something implied to be going on between him and Taffy.
The New Shmoo: the scams were always perpetrated by humans, but the Shmoo himself was some sort of magical creature.