Inspired from the cave stream, I think a haunted house (or any haunted environment) would be pretty good. Have Neuro tell ghost stories, get possessed from time to time, play spooky ambience like footsteps, creaking floors, distant screams etc. I'm not sure if it's possible or how difficult it would be do so, but having an animated background with things fading in and out would be pretty cool too. I think there's a lot that can be done with this.
We can have Neuro
or Evil Neuro
for this, whichever people prefer. I'm fine with either.