Were Shaggy and Scooby trying to rescue the girls from Revolta because they were worried about them, or because they were afraid of the fathers' punishment? In other words, were Shaggy and Scooby genuinely looking out for the girl ghouls' well-being, or were their actions motivated by what would happen to them if they didn't?
Is Scrappy as clueless as the Calloway Cadets about the girls, or is he just that unfazed by them? (Though he did recognize Sibella in her bat form)
Ear Worm: "Scrappy's Rap" is rather fun to bob your head to.
All the Cute Monster Girls for the Scooby franchise. They appeared only in this movie (and are the main reason for fans to rewatch it), but have gained a great popularity among the fandom.
The three new students who briefly appear at the end of the movie are also pretty popular, to the point where the fans have given them names: Mary (the alien), Goonie (the Creature from the Black Lagoon), and Godzina (Godzilla's daughter).
Just Here for Godzilla: Of the movies based on the "Scrappy Decade" in the Scooby franchise, this is the most fondly remembered, not so much for our heroes than for the Cute Monster Girls loved by fans.
Self-Fanservice: Again, the monster girls in the fanart. Especially Sibella.