Here's one of the most forgotten crossovers: GORGO #12, "Monsters' Rendezvous," in which Gorgo and his mom fight giant Venusian invaders. They get a little help from Reptisaurus, who came about after Charlton adapted the film REPTILICUS. Following the official adaptation, Charlton made up a new monster, "Reptisaurus," with his own title, so the company could do their own flying reptile-monster w/o paying the owners of the REPTILICUS franchise.
