If you're looking for examples related to a specific show or movie, see these:
- Scooby-Doo, Where Are You!
- The Scooby-Doo Show
- Scooby-Doo and Scrappy-Doo
- What's New, Scooby-Doo?
- Scooby-Doo! Mystery Incorporated
- Scooby-Doo Direct-to-Video Film Series
- Scooby-Doo! Haunted Holiday
- The Scooby Doo Project  . It's a parody of The Blair Witch Project. That should show give you a good idea. What makes it worse is it's implied the gang died at the end.
- One classic ad on Cartoon Network featured characters from Scooby-Doo: Shaggy showed up in a spooky castle calling out, "Scooby-Doo! Where are you?" This cut to Scooby on a tropical beach, saying, "Right here, Raggy! On Rartoon Network!" What was scary about it was not only the notion that Scooby would desert his friends in the middle of a case, but also the fact that Shaggy was barely animated at all, paralyzed and semi-slouched in seeming defeat as he called for help. It was haunting.
- The townsfolk (plus Daphne) turning into werewolves in the first episode of The 13 Ghosts of Scooby-Doo.
- The Ghouls getting Revoltized in Scooby-Doo and the Ghoul School, specifically their expressions: Sibella's eyes shrink as if she were going feral, Elsa looks like her mind just got fried, Phantasm quickly loses her Genki Girl composure and scowls for the first time in the whole movie and Winnie howls for some indiscernible reason. Elsa, Winnie and Tanis were freed early, but Sibella and Phanty remained under the spell longer. The former was freed by Tanis and apparently needed a few seconds to shake off the effect. Phanty, being under the longest, probably would've had more permanent effects had Scooby not knocked over random chemicals in the potion.
Tanis: Gee... you were under the hairdryer so long, you were getting cranky.
- In one of The New Scooby-Doo Movies episodes, the gang helped Dick Van Dyke discover that his circus was being terrorized by the strongman, sneaking up on the guy while he's working out. But the strongman reveals that he not only heard them, and demonstrates what he'll do to them by effortlessly twisting his barbel like a pretzel. This is not the usual greedy Scooby villain; this guy intends to straight up murder the gang.