Specimen 3 is a dark brown insectoid creature with a hard, shiny exoskeleton. Its body is similar to that of a centipede, while its face is more reminiscent of a spider's. Its body has four distinct segments, each with a pair of legs. Specimen 3's front-most segment has eight round, greenish eyes, and bears five sets of pincers.
Specimen 3 appears for the first time after the player reads the Generic Lab Assistant's note. The Assistant claims to have heard a clicking noise before dying. After reading the note and moving towards the exit, a clicking noise is heard, and Specimen 3 enters the room and begins to chase the player. It deals about 30 damage on contact.
During the chase, Specimen 3 creates holes in the ceiling from which it may drop down. It crawls instead of floating like previous Specimens, and moves at the same speed of Specimen 2.
It takes about 4-8 seconds for Specimen 3 to drop down from one of the holes in the ceiling to chase after the player.
Hitting Specimen 3 with the Axe will stun it for a few seconds.
According to the CAT-DOS, it was in testing before it escaped and killed the Generic Lab Assistant.
"WRITHING SNEEZES", Specimen 3's chase theme.
Sounds heard when Specimen 3 is near the player.
- Specimen 3 is inspired by the game Resident Evil.
- Specimen 3 is referred to in notes written by the generic lab assistant as "Subject 5", which has caused many people to be confused as to which specimen the lab assistant was talking about.
- In the lab that Specimen 3 broke out of, there are four creatures still contained. These are believed to be subjects 1-4.
- At one point, there was a bug where Specimen 3 would get stuck in the floor. This appears to have been fixed.
- In update 2.3, once the player died from Specimen 3, the game would crash.
- Specimen 3 doesn't have a death screen.
Specimen 3 has more body segments in the HD version than it did in the original game.
Differences from the original game:
- It is much faster.
- Crawls out of a hole in the ceiling just after the player passes under one.
- In rooms without a visible ceiling, it enters through the door.
- Can pass through Specimen 1.
- Upon dealing damage to the player, it crawls away, scuttles about in a circle, then resumes crawling after them.
- It is currently the only Specimen who should theoretically be faster than the player in the long run. While it is slower than a player at full sprint, it is fast enough to catch up with the player once their stamina reaches zero, as the stamina cannot regenerate fast enough. This is especially dangerous in extremely long rooms, where Specimen 3 can get an unavoidable hit.