- Mary's death in the opening scene, in which she is slowly burned alive onstage.
- Jess's death. Mary uses her supernatural abilities to wrap her cape around Jess's neck and drag the screaming girl across the room. At first we are led to believe that Mary will use a blade to decapitate the poor girl (whose neck is already clearly wounded from the cape) but she apparently changes her mind and opts to hang her instead. Then, as one final "fuck you" to Jess, she proceeds to chuck her out the window and onto the grass. We then cut to a shot of her lifeless eye, before the camera pans out to show her mouth covered in blood.
- That damn horse. The lifelike tongue, red eyes, and the way it slowly turns its head to look at Vicky make it plunge into the Uncanny Valley.
- In the same scene, there's the way Vicky is trapped under her own blanket, able to do nothing but scream.
- Vicky being pulled into the chalkboard, which turns into a pool of some strange liquid.
- The cafeteria scene, where the lighting becomes sickly and seedy, cockroaches can be seen all over the damn place, and the slop being served as food contains Mary Lou's floating head.
- Mary's murder of Father Cooper. As Bill later discovers, she took a pair of scissors and shoved them down his gullet.
- Josh's rather violent death by electrocution. His face boils off while he's still alive, screaming in agony.
- The entire sequence of events leading up to Monica's death. What starts out as apparently nothing more than shallow Fanservice turns into one of the most tense scenes in the movie, as Monica is reduced to hiding in a locker while Mary stalks the room in search of her. Just when it seems as though she's in the clear, Mary uses her powers to crush the locker with Monica still inside.
- Mary's reemergence at the prom. The image of her hand reaching out of Vicky's open chest is disturbing enough, but the sight of her charred corpse is utterly haunting.
- Even after her body is fully restored, her laugh will send chills down your spine.
- Mary in general is just a deeply unpleasant character. Some viewers may initially sympathize with her due to her painful death, but as the movie goes on, it becomes clear that she is truly a monstrous psychopath.
Nightmare Fuel / Hello Mary Lou: Prom Night II