Old obscure video game here, but the hostile alien that doesn't appear until the deeper levels of the only atari 5200 game, Rescue of Fractalus sent me screaming out of the room when I was a kid.
The game is pretty quiet, with a lot of periods of complete silence. you fly around rescuing downed pilots in a rudimentary 3D flight sim. In the earlier levels, its pretty easy.
!. land near enough to the crashed ship and get a notification (you may or may not be facing it, so what you see may vary
2. You turn off your shields while the pilot runs to your ship (if you don't, the pilot fries when they try to knock on your airlock)
3. pilot knocks on your airlock and you open the door (if you don't, their knocking gets gradually weaker and eventually, the pilot dies)
4. Pilot enters your ship, you close your airlock and you turn your shields back on before taking off and going onto the next (or heading for the mothership if you have enough to complete the level. Different pilot ranks have different colored helmets and are worth different amounts of points.
All well and good until 6 year old me was doing REALLY good on a run and got to like level 12 or something for the first time. I landed my ship near a wreck and settled in for the wait and suddenly there was a loud noise and this motherfucker popped up on my windshield and started pounding on it. I later came to learn that green helmeted pilots are aliens (which means nothing if you land facing away)
If I hadn't dropped the controller and ran screaming from the room, turning the shields back on would have solved the problem, but that shit had me shook for days
Here's a video of my childhood trauma