This article contains content that either was in the game, or was originally planned, but not used in the game.
Sparky is an unused monster. He was one of the concepts for the first monster that was eventually going to be the Brute, though he was scrapped as he was simply too enormous to move through the corridors and doorways effectively. He was then turned into an A.I test monster, and dubbed Sparky.
Team Junkfish have stated that they may consider tweaking Sparky and bringing him into the game as a fourth monster, though nothing is currently planned.
The Stalker Edit
The Stalker was the original name for the Hunter. It followed the same concepts, lurking around in the vents, preparing for a strike, though it was supposed to have much different A.I. It was going to follow a "scent trail" that the player would leave, and which would build up over time. It was also supposed to have a strange attraction to electricity.
Walkie-Talkies were distraction items that could be found by the player in various rooms.
They spawned in pairs, and one of them could be dropped in an area, while the player called it with the second one, luring the monster over there (basically a portable Engine Room phone system.) The Walkie-Talkies had a limited range, which meant that they could not call each other if they were too far apart.
They were removed in patch v.0.9.3 as they caused performance issues, and had multiple bugs.