Place it at the end of a slow build, just after the fog appears and before the reveal, then follow it with a scream for contrast and finish with a reaction clip to let the joke settle.
About this sound
This 12-second clip pairs the phrase about fog arriving with a long, unsettling laugh that builds and lingers. It feels creepy and playful at once, like a joke told just as the lights dim, and it works because the laugh keeps going after the words stop.