The CAT-DOS is a special device that can be randomly found in some rooms in Spooky's Jump Scare Mansion.
The CAT-DOS is a group of three large cubic computers, sitting between two doors near the end of the room. The one in the middle has a red screen and a small keyboard, with the other two having blank black screens. Only the middle one can be accessed.
It is a mysterious computer that contains information about many of the Specimens running rampant in the mansion.
Upon examination, the player will see on its red, faintly static monitor the first two following options: 'ENTER' and 'EXIT_PROGRAM'. The player can choose 'ENTER' to continue to the next menu, in which with three new options are available: 'ACCESS_SPECIMEN_DATABASE', 'MODIFY_HOUSE_LAYOUT' and 'BACK'.
The 'ACCESS_SPECIMEN_DATABASE' option will bring the player to another menu, in which there are entries for all Specimens that appear in the normal game. Specimen 1 to Specimen 5 are available all the time. After about 300 rooms, specimen 6 to Specimen Specimen 11 become accessible by selecting the "Next" option, though the real entry for Specimen 10 can only be accessed once the player has made it through Room 500; If they have not done so, CAT-DOS will just open the old Specimen 10's entry. Specimen 9 appears as 'Specimen __' and, sometimes, its entry will not open.
Attempting to select the 'MODIFY HOUSE LAYOUT' option will only give an error screen.
There is currently a rare chance upon opening the CAT-DOS screen, a random Specimen will seemingly start a chase and play its theme on top of the CAT-DOS ambience sound, and also produce its sounds loudly as if the Specimen was close to the player.
There is a bug that if the player accesses and exits CAT-DOS during room 501-509, the room number will say 502 instead of the room the player originally entered.
In the HD Renovation Version, Specimen 5 and 6's method of attack are swapped. It is currently unknown if this is a bug.
From room 900 onward, when you open CAT-DOS, try to access 'MODIFY_HOUSE_LAYOUT' six times and then open Specimen 9's entry, you will enter a secret menu showing the entries of Specimen 9 Boss Mode and four unknown Specimens named: The Mattress Man, The Dolphin, Lines and Paina. It appears that all of the Specimens are active except Paina, who is still in development.
- CAT-DOS is a reference to the operating system MS-DOS.
- The secret CAT-DOS entry for The Mattress Man is a reference to the Gmod map Shadows Chapter 3 which was made by Akuma Kira himself. Proof for this is saying that the monster is "just An Invisible Fast Zombie with a box welded to it". The fast zombie is an enemy from Half-Life 2 and a spawnable NPC in Garry"s Mod.
- The CAT-DOS entry for The Dolphin is also a reference to a Garry's Mod map Akuma Kira made.
- Paina's secret entry is a reference to the game Akuma Kira's Day Off.
- Lines is a reference to horror game Space Blaster (Lines) made by Akuma Kira.