Place it at the very end of a build-up, right before the reveal or punchline lands. Follow it with a sudden suspense sting if the moment stays tense, or let a laugh track style reaction take over if you are turning the scare into a joke instead.
About this sound
A very short music box rendition of Pop Goes the Weasel, played on a thin, tinny mechanism that cuts off in just over a second. It feels sweet on the surface but quickly turns uneasy, like a warning that something is about to jump out. The cue comes from Five Nights at Freddy's 2, where it is tied to the Puppet.