I accidentally discovered how that "U'weh, weh, weh, weh" sound (just before the bats show up) at the start of the original Scooby-Doo intro works. It's a really heavy Wah-Wah-- I don't know the exact settings, other than my guess that it uses high resonance, low depth, and an LFO frequency of about 3.4Hz-- but that's definitely one of if not the effects being utilized there, surely.