It's not October as of writing this (oh no), but we can still do a spooky thing. This mod makes a skeleton gif walk over the screen every time the scary vanilla ambient cave sound plays. If you put this in your friend's mod folder, they'll find out the fun way (evil), tho this is not really a screamer, just spooky.
This mod is technically resourcepackable. If you for some reason want to make one, you need to follow the file structure in the repo and make a spritesheet out of the gif/video frames.
A femur for Aaron for the idea:
