Put it just before the reveal in a reaction edit, then follow it with a Vine Boom Sound Button for the impact and a Dun Dun Dun Sound Button when the twist turns serious.
關於此聲音
This clip is one voice holding a single ahhh as a long, high-pitched cry for about nine seconds. It feels like pure comic panic, the kind of exaggerated shock that makes a small surprise seem huge and gets a laugh before anyone has time to react.