Duke Nukem 3D might be a light-hearted, over-the-top and comical parody of countless action and sci-fi movies, but don't let that fool you. It still plays enough sci-fi and horror tropes straight to be creepy and even frightening at times.
- There are naked women trapped in alien plant matter throughout the game, who mutter "Kill me" in a desperate tone when talked to; it's a bit creepy, but soon you get used to it. All you can do is either kill them or leave them to their fate. Even worse is the poor woman in the intro in Episode 4: The Birth. As if being impregnated and giving birth to the alien's new Queen isn't bad enough, there are alien troopers surrounding her, watching with joy as she screams in agony and presents them with their abomination of a ruler.
- The Assault Commander. "Suck it down!" "Boom!", Duke gets reduced to Ludicrous Gibs. Not to mention their creepy heavy breathing, and the fact that they appear to be shooting those rockets out of their rectums.
- The Protector Drone. Horrific appearance and sound, loves to hide in dark areas where its glowing red eye is the only thing visible, moves like grease lightning and attacks with shrink rays.
- Another Demonic Spider: the Protozoid Slimer. A Face Hugger Expy which after attacking blocks the screen, allowing you to see him munching on Duke's face. They're hilariously wimpy and barely deal damage unless you panic and fire the RPG when one's on your face (And ending up killing yourself), but that doesn't stop a good handful of players from jumping in their chairs or outright scarequitting the game upon sight of one that isn't even close. Add to this the fact that the first level, and indeed most of the levels they appear in, lack much in the way of lighting.
- Not only you should fear the Protozoid Slimer, there's another one that's quite worse: The Sentry Drone. This abomination is a fast, intelligent, flying metal sled, bearing a creepy "smile" on it's face in which will charge and suicide bomb RIGHT IN YOUR FACE! While they're not quite durable as it seem, but their charging attack will cause severe damage towards Duke, specially in the harder difficulties. Next time, if one of those bastards charge towards you, you're in for a world of pain.
- This example is somewhat of a mix between Nightmare Fuel and Fridge Horror: You cannot see any Pig Cops in the Lunar Apocalypse episode, which makes sense In-Universe since they are L.A.P.D. cops mutated, and outer space isn't exactly within jurisdiction for Los Angeles's finest. You can, however, find one Pig Cop in level 8 (Dark Side), lying dead on a table with surgical equipment nearby. Why (and what for) were the aliens experimenting on a mutated human being?
- Octabrains. They look hideous (complete with a built-in Slasher Smile), make creepy noises, are tough to kill, and seem to love sneaking up on you. Oh, and they're mostly found in dark underwater areas, along with Protozoid Slimer eggs and trapped women.
- Lunar Apocalypse is arguably the creepiest episode of the game, mainly because it's played a little more seriously than the others (well, except for the ending cinematic) and is generally lacking in parodies and gags. It's just you and a ton of aliens in abandoned, often dark facilities, in the middle of the inky blackness of space. Stand at one of the many windows, look out at the Earth, and just try not to feel a little isolated. Oh, and this also happens to be the episode where the Assault Commanders, Sentry Drones and Protozoid Slimers are introduced.