I participate in a electronic mailing list. This means that once a day (or so) in my e-mail account there is deposited a collection of commentary by other participants in the list. It's a bit like a cross between having a lot of pen pals and a private BBS. Recently something that sparked a discussion was using Cthulu dieties in a Wiccan format. As it happens, there is a guy who each year at minicon puts up posters advertising "Cthulu Wicca". It's a pretty hilarious joke. Some of the people on the mailing list didn't seem to see it that way, and started listing off entitiy names they had used in ritual and asking for source material. I like to think I'm a creative person, but I really don't see how the Wicca and the Cthulu mythos can be reasonably combined.
What I know of the Cthulu mythos comes from three places; 1-AD&D's first edition of the "Dieties and Demigods" book, which contained an unauthorised gameing usage of the Cthulu mythos; 2-The Call of Cthulu Role Playing Game, which was an authorised version, and 3-the stories of H. P. Lovecraft, which were the inspiration for it all in the first place. The mythos itself is presented as being so alien as to 1-be completely evil in effects and 2-eventually kill, mutate or drive insane any who come into connection with it. The first is presented as the most desirable, and the three are not mutually exclusive.
Wicca, as I have studied, understand and practice it, aknowledges and respects the reality of God and Goddess and magick, and develops a real and personal connection with the dieties.
For someone to be willing to combine the two, seems to me to imply only a few possible attitudes.
Wicca is real, but Cthulu is not: This would be a person who wanted a real relationship with the divine, and used names from the Cthulu pantheon for some weird reason. This seems disrespectful to one's path in the extreeme; why use Wicca to have a realtionship with a God that isn't really there. If this person isn't taking Wicca seriously enough to want to experience connection with real diety (and not what they have made up or redifined as convenient) they why do it at all? This is the sort of person who calls Kali a "mother Goddess".
Cthulu is real, but Wicca is not: This is a person who likes the idea of playing around with dangerous powers, but since there is no real, contact, thinks they run no risk. This is either not a spiritual person at all, or somebody on a path that is really not working for them. If someone doesn't take their dieties seriously enough to seek connection with them, then how and more importantly why relate to them at all? This is the sort of person who would have a coronary if a DDM actually worked.
Both are fake: This is the goth-chick (or guy) who likes to play with a spooky path, and spooky diety names, but doesn't take any of it seriously. I wouldn't be surprised at this person having chosen Wicca to be able to say "ooh I'm a *witch*", and having chosen Cthulu to be able to brag about how gory their gods are. This is similar to the person who says "I'm a Satanist" and when pressed, admits that they don't really worship or believe in Satan, they just want to irritate fundamentalist Christians.
Both are real: this is a person who is insane or suicidal, or aiming for both on some level.
The 'I don't know' factor: This is a newbie being let into this by someone else who tells them that all the horrific lore is really there to keep the "wrong people" from learning the "real secrets". This person is a fool, or severely unfortunate in choice of mentors.
Perhaps there is some resepectful, serious person out there who is working with "Cthulu Wicca". I doubt it.
Oh there is one last possibility. It's a joke. Which it is, and actually it's a pretty funny one. But just in case (insert spooky music) consider this a warning from all those who found out the truth too late, and are now in no condition to express how very wrong and foolish they were......