One of my favorite /tg stories from back in the chan of 4 days was about a Call of Cthulhu game. Basically one of the characters was an investigator and was looking at a crematorium and noticing some dog-tracks when the Gm had the player check and discover that the only way those tracks would make sense is if the dogs were walking on their hind legs.
So by the proxy of the game, anytime something weird happens you gotta roll sanity. So the player rolled…and critically epic failed. Which led to a situation of a guy going from full mental health to trying to stuff himself inside the cremation machine screaming “Two legs! TWO LEGS!”.