Tom Sutton, under the name "Sean Todd," did four installments of a series called "Frankenstein Book II," appearing in issues #3-6 of Skywald's PSYCHO b&w magazine. It's very incoherent, mixing monsters of different eras, and doesn't have an ending, but the artist puts a lot of moxie in his pencils.
In WOW #14, Mary Marvel meets both the folklore-character Jack Frost and an approximation of the Greek dawn-goddess Eos, under her Roman name Aurora.
The Egyptian wizard Ibis encounters both Celtic and Greek boogiemen in IBIS #4 when he squares off against both Morgan LeFay and Cerberus.
I've now reviewed both the 1995 and 1997 narrative incarnations of the DARKSTALKERS franchise here.
In addition, two episodes of the 1995 TV show sustain a crossover-vibe. In "Donovan's Bane," the episode that introduces the monster-hunter Donovan Baine, the spirits of both Merlin and Morgan Le Fay briefly appear to lend aid to their respective descendants, Harry Grimore and Morrigan the Succubus. And in "Darkest Before the Dawn," regular vampire Dimitri is revealed to have been in contact with the O.G. King of Vampires, who appears in a flashback to give Dimitri an idea that becomes the main story of the episode.
JUSTICE LEAGUE UNLIMITED #14 did its own version of "the Trenchcoat Brigade," even though most of the characters aren't wearing trenchcoats. This version includes Deadman (occupying the body of Wonder Woman in this scene), Doctor Fate, Doctor Occult, Zauriel, Zatanna and Etrigan the Demon. These weirdie-heroes get the lion's share of action while the regular JLU heroes sit things out.
Scene from the debut story of the Little Chief in PEP #40. At least he makes his bones by punching out a mountain lion.
The 1990s MASK cartoon had at least one villain-crossover, the half-hour "Convention of Evil." At least six villains-- Pretorius (Tim Curry), the Stinger (Stuart Pankin), the Tempest (Bud Cort), Lucifer (Jonathan Harris), Kablamus (Jim Cummings) and Gorgonzola the Cheese Witch (Cree Summer) -- had already appeared on earlier episodes, as is illustrated by clips from those shows.
