All of the monsters in question are unique to AD&D, and as I wrote virtually all of their stats and descriptions they are in fact my creative products, not the IP of WotC. That's a FWIW.
While a few of the critters in questions are purely products of my own imagination--carrion crawler, gelatinous cube, roper for instance--there were many sources of inspiration for the majority of the monsters, and I will name a few:
Drow: A listing in the
Funk & Wagnall's Unexpurgated Dictionary, and no other source at all. I wanted a most unusual race as the main power in the Underdark, so used the reference to "dark elves" from the dictionary to create the Drow. (And nary a one has crow's feet).
Troll: "The Three Billygoats Gruff" where the Great Ugly Troll has a nose as long as a poker and
Three Hearts & Three Lions most assuredly.
Ogre Magi:
General Raiko and the Ogres of O-E-Yama, a beautifully illustrated children's book translated into English from Japanese.
Shambling Mound: Strictly from "The Heap" in
Airboy Comics, of which I was a great fan.
Displacer Beast: From A.E. van
Voght's Voyage of the Space Beagle.
Kuo-Toa: These were not inspired by any particular literary source but made up out of whole cloth by me.
Bugbear: The name comes from folklore, but the remainder is my creation. When I told the artist that it had "like a pumnpkin" he took it literally rather than as figurative for a large, oval head.
Lich: Right on in regards to Gardner Fox. Gar and his wife Linda were friends of mine.
If anyone reading this thresd has specific questions I'll be happy to answer them.
Cheers,
Gary