"A Halloween Hassle at Dracula's Castle," a 1984 episode of THE NEW SCOOBY DOO MYSTERIES, joins the ranks of a small coterie of Scooby-stories featuring a mashup of classic monsters.
Dracula and his assistant Igor (on loan from a Frankenstein movie, perhaps) encounter the Scooby Gang and invite all of them to Drac's castle for a costume party. However, the Scoobies are the only ones who wear costumes; everyone else-- Drac, his unnamed bride, a mummy, a wolfman, a gill man, an invisible man and a Frankenstein Monster-- is the real thing. The monsters have all retired from scaring people, but now they're being haunted by the ghost of Drac's old foe Professor Van Helsing, so they want the famed Scooby "ghostbusters" to bust that boogieman.
It's not surprising that the ghost is the only phony monster in the bunch, an imposture of Igor, who wants the castle for himself. In a peculiar side-plot, the only non-monstrous guest of Dracula is a lady stage magician named Chandra, who aspires to get hold of a mystic gem that will (and does) give her real magic powers. At first I had no idea what a stage magician was doing in a monster-mashup. Then I learned that the writer of the episode was Paul Dini, who, according to fandom lore, was a big fan of the DC Comics magician-hero Zatanna-- so much so that he worked her character into an appearance or two on the BATMAN and JUSTICE LEAGUE cartoons, not to mention the fact that he later wrote a ZATANNA comic series.
"Hassle" also counts as a crossover because Dracula and the Frankenstein Monster are definite icon-emulations of their cinematic personas, though all the other monsters are just generalized monster-types.