Well my holy grail was apparently never even released. I always wanted Cy (the big white monster thing in the video:
https://youtu.be/mLnZ04r9Z1g) when I was a kid, but I came to the 1991 Land of the Lost party too late as a child. However, I started digging around for this toy, and the only place I've found him is in these old ads. Collector's checklists don't even mention him.