Put it immediately after the unexpected reveal, before any commentary resumes, then follow it with a Vine Boom to underline the moment, or open with a Dun Dun Dun beforehand to build tension before the question lands.
About this sound
This is a short two-second spoken outburst asking what just happened, delivered in a startled, incredulous voice that rises as if the speaker cannot believe what they have just seen or heard. It feels abruptly shocked and confused, with a comic edge that makes a strange moment land harder, turning sudden weirdness into a shared reaction instead of leaving it hanging in silence.