Scooby Doo and Secular Humanism

[Malthus]

Yeah, that's correct.  It just that it didn't happen in the original version of the show.  It happens with some regularity in some of the latter versions, and in some versions, it turns out that the main plot wasn't a hoax at all--for example, in both the theatrical live-action movies, some of the supernatural elements of the case turn out to not be hoaxes.  (Though I suppose that both could be considered SF rather than supernatural, particularly the 2nd movie, but it's the kind of SF where the science is so weird or crappy that it might as well be magic.)

Well, can't prove it without reviewing old episodes, but I remember this happening and I only ever watched this cartoon as a kid in the 70s.

[dps]

Yeah, that's correct.  It just that it didn't happen in the original version of the show.  It happens with some regularity in some of the latter versions, and in some versions, it turns out that the main plot wasn't a hoax at all--for example, in both the theatrical live-action movies, some of the supernatural elements of the case turn out to not be hoaxes.  (Though I suppose that both could be considered SF rather than supernatural, particularly the 2nd movie, but it's the kind of SF where the science is so weird or crappy that it might as well be magic.)

Well, can't prove it without reviewing old episodes, but I remember this happening and I only ever watched this cartoon as a kid in the 70s.

Well, the first 4 series in the franchise all aired before 1980, so it's very possible that you saw what you describe on Scooby-Doo in the 70s, just that it was in the 3rd or 4th series, not the 1st (not sure if it ever happened in the 2nd series--actually, I'm not sure either way about the 3rd, but I do know that what you describe definately happens in the 4th).