In the episode The Dark Baptism, Aunt Hilda says Sabrina’s dad could have been a movie star, like Cousin Montgomery.
The fifth episode is called "Dreams in a Witch House", referencing the famous H. P. Lovecraft short story "Dreams in the Witch House". The Monster of the Week for that episode is essentially a Composite Character of Pinhead and Freddy Krueger via being a demon released from a puzzle box that can twist people's dreams to its will.
Sabrina's red dress is copied from Rosemary's Baby, and there's also a doctor called Dr Sapirstein.
"An Exorcism in Greendale" has plenty to The Exorcist, such as the possessed attacking with projectile vomit.
Daniel Webster is a not-so-subtle allusion to Stephen Vincent Benét's short story, "The Devil and Daniel Webster."
The Academy of Unseen Arts can be considered a Shout-out to The Unseen University and its Tower of Art, the main wizarding school in the Discworld.
Harvey is shown in bed wearing a white crop top with the number 10 and watching a movie in bed with his headphones on mirroring Johnny Depp's appearance in A Nightmare on Elm Street (1984), the only difference is Harvey is watching it on his laptop instead of a small TV.
During the exorcism of Jesse Putnam, Zelda calls out the Spellman ancestors to finally break the tie they are stuck in with Apophis, one of the names she calls out is Evanora.
When Principal Hawthorne returns and summons Sabrina to his office, Roz looks up and says He's baaaaaack.
During Ambrose's first appearance, he's wearing a purple shirt with the message"Aloha From Hell".
The teenager that Madam Satan sacrifices to bring back the Thirteen has the surname Loomis, a reference to the Scream and/or Halloween series.
Numerous Clive Barker paintings can be seen throughout the series, including in Suzie's bedroom and Father Blackwood's office hallway.
The glass ceiling above the Spellmans' living room resembles the one from Suspiria (1977).
Aunt Zelda and Father Blackwood both make a point of describing the path of Satan as delicious.
Gryla's backstory references the story of the two starving mothers in the Books of Kings.
Several teachers at the Academy of Unseen Arts share their surnames with horror authors, including Brother Machen, Brother Lovecraft, Brother Bierce, Brother Barker, and Sister Jackson.
In episode 12, Blackwood takes some of the male students to a gentleman's club called Dorian's Gray Room — named for its proprietor/bartender, Dorian Gray.
At one point Harvey compares Sabrina's newly acquired über-powers to The Dark Phoenix Saga, going into great detail about the plot because Sabrina hasn't got the faintest idea what he is talking about.
In the season finale, Sabrina utters the phrase "Not today Satan, not today!", originated by Bianca Del Rio.
While Theo and Harvey are exploring Mine 13, Theo starts talking about the movie The Descent, remembering about that movie now that they are in a dark cave.
The way the Mandrake copy of Sabrina grows out of a plant while she sleeps, tries to copy others the same way, and expresses its displeasure by pointing and screeching is a reference to Invasion of the Body Snatchers (1978).
In Harvey's vision he attends a university in Arkham, where he meets a haunted artist named Howard. It's quickly revealed that Howard has nightly visions of demons and eldritch entities he calls his muses, which he paints in the hopes of slowing their awakening — all references to H. P. Lovecraft and the Cthulhu Mythos. One of the entities painted is even Cthulhu itself.
The physician who checks up on Tommy after the accident is called Doctor Phibes.
Possibly unintentional, but The Inquisition in Chapter Twelve very quickly starts to resemble a scene in Damien: Omen II. In both examples a student is rigorously quizzed on dates relating to their class by a teacher trying to make an example of them, while receiving supernatural help with the answers. The dialogue also very closely mimics a nearly identical scene from season 1 of The Vampire Diaries which involves the same scenario (though, being a vampire who was alive for the events he's being quizzed on, the student actually just knows the answers) and was likely inspired by the same film.
In Season Two, Blackwood summons a Deep One from the depths of Loch Ness, and is granted an egg he says will birth a horror, ranting to Ambrose and Prudence that the Old Gods and Eldritch Terrors are coming — all references to the Cthulhu Mythos.
The means by which the Pagans summon the Green Man are largely a shout-out to The Wicker Man, the effigy being a giant man of sticks and the fact that a virgin is needed for the sacrifice. Dialogue from the film is even quoted by Miss Wardwell, possibly foreshadowing that she is actually someone else putting on an act to convince those watching.
During the 3rd part of the Hell Rulership quest, Sabrina is sent to talk with one of the 3 greatest traitors, Judas, (Brutus and Cassius are also there) just like Dante's Inferno.
The Pagan leader introduces himself as Professor Carcosa, and if that is not unsettling enough, his real identity turns out to be The Great God Pan.
In a shout-out to Pet Sematary Prudence is on guard at the Spellman House, where she encounters Agatha who is covered in blood and says „first I played with Dorcas now I want to play with you“.
The Darkness assumes the form of a series of soot-covered miners who desire light. Just like the Woodsmen in Twin Peaks.
Lucas Hunt's transfer from Innsmouth High is a pretty obvious one.
The entirety of the Cosmic universe is one to the original Sabrina the Teenage Witch, complete with the actors who played the aunts in the original series.
When Sabrina is convincing Caliban that he has to be gelded to marry Sabrina Morningstar, Prudence draws a shark knife with a unique hooked blade; both the knife and the situation refer to an early scene in Planet Terror.
