Place it at the exact cut where the unfamiliar face first appears, before any response line. Follow it with the Metal Gear Alert Sound Button for a spotted moment, or precede it with the DJ Airhorn Sound Button for an over-the-top entrance.
About this sound
This clip is Zim's voice asking 'who are you?' in a short, pointed question. It feels suspicious and confrontational, like an alien challenging an intruder who does not belong. It comes from the animated television series Invader Zim, where he reacts to strangers with immediate distrust.