1. Frozen, Tangled, and The Little Mermaid all exist within the universe.
2. One of the snuff filmmakers in Elsa's storyline of AHS: Freakshow is a young Dr. Arden from AHS: Asylum.
Dr. Arden's backstory featured him as a Nazi doctor in WWII, and he did, after all cut off Shelley's (Chloë Sevigny) legs in Asylum which is exactly what the snuff filmmakers did to Elsa in her Freakshow flashback.
3. Calhoun's backstory in Wreck-It Ralph is even more tragic than you thought because she doesn't kill the cybug who eats her husband, she kills the mutated version of her husband that the cybug immediately starts evolving into.
Remember what happened to King Candy after he was eaten by a cybug? Girl had to straight up murder her husband on her wedding day.