In Chapter 1: New Arrivals, when playing on a completed save, if the player breaks the light air vent on the left side from a different room from the Flight Lounge, a Necromorph will suddenly appear, but will not trigger a cutscene, causing the game to glitch and allowing Isaac to humorously lead the Necromorph around the Flight Lounge as the crew does not notice the intruder.
Contributed by ProtoSnake