Be careful.exe and turn back.exe
There are two M.U.G.E.N mods that were made to be creepy, called "be_careful.exe" and "turn_back.exe." I will be talking about both in this same article, as both mods are very similar.
be_careful.exe
be_careful.exe has a WinMUGEN title screen without text. It's only character is ".EXE" which is a Sonic.exe edit that performs these actions exactly: 1. It opens it's eyes, and then closes them again. 2. It floats up, and then teleports away. 3. The original Sonic.exe jumpscare pops up, and 10 frames after, the game crashes. It is unknown who created this project. The only information I can get is the name of the screenpack's creator, which appears to be "666" but that's all I can find.
turn_back.exe
turn_back.exe's title screen has no text or background. It's only character is "William...?" which is essentially William The Hedgefox without a tail and with blank eyes. It performs the same exact actions as ".EXE" but instead it shows a spooky Ronald McDonald image. The project's creator seems to be the same as be_careful.exe's creator.