- Development Gag: Doing the CAT-DOS Easter Egg will give you four new Specimens to look at, and two of them, "the Mattress Man" and "the Dolphin Man", were based on old creations from one of Akuma Kira's Garry's Mod episodic maps, "Shadows". "Lines", meanwhile, takes from Space Blaster, a game by the developers which partially inspired Spooky's Jumpscare Mansion.
- Easter Egg: A lot of these exist. Notably, Akuma Kira has revealed the existence of a pretty hidden one, involving various CAT-DOS entries.
- Fan Nickname: Specimen 8 is generally known as the "Deer God".
- Thanks to her Leitmotif, Unknown Specimen 5/Lisa has earned the nickname "The Moaning Lisa".
- Specimen 6 often finds himself being called "Ben" or "The Merchant".
- Specimen 4 being called "Ringu" is especially common, given it appears in the game data.
- Monster 6 falls into the same category as Specimen 4, except as "Bekka".
- Schedule Slip: The initial February 17, 2017 release date for the HD Renovation edition was changed to the 24th, because the creators didn't want to release an unfinished product. It was then released on the first of March 2017 instead.
- What Could Have Been:
- At one point the Dev uploaded potential Specimen 4 appearances on his DeviantArt. Aside from the one that was made official and a slightly edited version, two of them◊ featured Full-Frontal Assault (with Barbie Doll Anatomy and one of them having inverted colors).
- The developers considered outright removing the Old Specimen 10. They opted to instead turn it into a Bait-and-Switch Boss.
- Why Fandom Can't Have Nice Things: Fans wouldn't stop bugging the devs about adding a monster based on the Fazbear animatronics, so they deliberately made it bad just to spite them.
- The Wiki Rule: The game naturally has one here.
Trivia / Spooky's Jump Scare Mansion