@Princess♠Molestia
The Cthulhu mythos is something of an obsession of mine, and I certainly think something like that can work, although I would not peg Cthulhu as Pinkie Pie’s uncle. No, that would be Nyalathotep, the Crawling Chaos, the Bloody Tongue, the Black Pharaoh, the Haunter in the Dark. He’d be more Pinkie’s speed I think.
I actually have a few ideas for a Cthulhu mythos/MLP crossover.
Shadows over Ponyville: This would be my parody of H.P. Lovecraft’s somewhat overwrought writing style and his comical levels of racism. A unicorn OC, not dissimilar to his assorted self inserts in that he’d be a young, bookish, celibate gent goes to Ponyville and manages to mistake the town for an Innsmouth style cult city, thanks to those degenerate mud ponies and their coarse, vile ways.
Blessings of the Harvest: Applejack and Big Mac inducting Bloom into an ancient family ritual, a sacrifice to Shub Niggurath to ensure a bountiful harvest. Why do you think they keep pigs? This could essentially be a coming of age story for Bloom, as she desperately tries to save the hog marked for the slaughter from her own family members.
The Outsider: Essentially a straight retelling of one of Lovecraft’s stories. Our narrator has lived his entire life in a subterranean realm and longs for contact. One day he decides to climb a tower which opens up into a crypt on the surface world, blunders into a party, terrifies everyone and is horrified by his own reflection. The twist in this case is the surface world is Equestria and the narrator at the end describes his own human form in the most unflattering and alien ways possible.
I could keep going for awhile on this honestly. As I said I’m a great fan of the Cthulhu mythos, and even if his writing style is a bear to get through and his racism almost comical I still do love Lovecraft.