* The exact nature of the crew of the Cygnus. [[spoiler: Lobotomized by Reinhardt into [[{{Brainwashed}} mindless, subservient drones]] who can only continue to perform their tasks aboard the ship.]]
* The ending of the film with regard to the crew. [[spoiler: The last we see of [[BigBad Reinhardt]] and [[TheDragon Maximillian]] is Reinhardt's eyes darting madly to and fro from within Maximilian's visor, undeniably insane, as the new entity rules over the wreckage of the Cygnus, ''and its mindless, but entirely innocent crew'' in what looks to be a [[FireAndBrimstoneHell massive fiery cavern]].]]
* The line graphs used to represent the titular space anomaly in the trailer, due to it looking so plain ''[[UncannyValley unnatural]]'' and being superimposed over the more terrifying moments of the film.
* Just the brief glimpse of the "humanoid-robot's" face [[spoiler: when Durant removes the reflective faceplate; although still clearly alive, the crewman's face almost looks like a corpse, and the eyes seem on the verge of hemorrhaging. That little raspy breath he lets out upon being unmasked doesn't help, either]].
* [[KillerRobot Maximillian]], just by himself, is a perfect example. Between the [[ThisIsADrill whirly-blades]], [[ImmuneToBullets immunity to]] [[FrickinLaserBeams lasers]], some [[FrickinLaserBeams lasers]] of his own, a [[CyberCyclops single]] [[GlowingEyesOfDoom glowing]] [[RedEyesTakeWarning red eye]] with a particularly intimidating furrowed shape, the menacing hum of the servos as he moves, and the way he just [[ImplacableMan keeps coming]] while [[{{Flight}} completely ignoring terrain]], [[spoiler: and eventually [[TurnedAgainstTheirMasters engulfs his own creator]] and [[{{Satan}} presides over hell itself]],]] how could you not have nightmares for years afterwards?
* Maximillian's [[ThisIsADrill execution]] of Durant, which prompts Reinhardt himself to beg for protection from his creation. (Although he might just be playing the sympathy card -- he curses out Maximilian for killing Alex, but Alex ''had'' just found out Reinhardt's secret.)
* Dr. Reinhardt's pleas to Kate to protect him from Maximillian are another case of NightmareFuel should they be taken at face value, considering the possibility of spending decades practically all alone and having to look constantly over your shoulder to make sure your physically superior [[TheDragon Dragon]] isn't trying to kill you.
* What makes this all the more unsettling is that the movie was produced by ''{{Creator/Disney}}!''
* The heroes desperately fleeing across a flimsy gantry that's dwarfed by the huge fiery meteor that's rolling towards it.