I'm not a big Mythos fan. The names leave me baffled. Played CoC back in the day, always as a player not a GM so was just a casualty of various entities .
Read a small number of Lovecrafts books, so very familiar with the creatures met in those but not everything else.
Gug. Yes, knew the look, never met the monster LOL. Attached is an illustration by my chum T Ackland.
The main drive to doing these Cthulhu creatures is to go with Dracula's America 'Forbidden Power'. The author introduces a number of Lovecraft beasties to the game, and the shoggoth (Gibbering Spawn) is one of them. It has to fit on a 50mm round base in the game. To do a pulsing amoeba the size of a subway train would just be over kill for a Cowboy Skirmish game, I was never going to do that.