Place it right after the returning character is revealed, then follow it with the Law and Order dun dun sting to underline the twist, and save the DJ airhorn for the moment the crowd reacts.
About this sound
This is a short spoken line lasting just under six seconds, delivered as a quick burst of disbelief as the speaker reacts to someone returning once more. The rising, incredulous tone makes it feel funny and startled at the same time, like catching a familiar face walking back in when you thought they were gone for good.