The Demonic Head Shake is a staple of horror movies of recent history, made famous by the 1990 movie Jacob's Ladder. The effect is achieved by filming somebody (or something) waving their head at a very low frame rate and later play the footage back at normal speed which creates an unsettling motion blur effect. Characteristically, the shoulders and the rest of their body remain completely still while the head goes all jittery.
This effect can be used during a Transformation Sequence or alongside a Marionette Motion where awkward body motions are filmed in Adrenaline Time creating the illusion of a broken doll. Compare Exorcist Head when someone spins their head around 360 degrees.
- The Trope Maker is most likely Jacob's Ladder, which has The Vietnam Vet Jacob encounter several of those "twitcher" characters, signifying his mind slipping into madness. The most famous scene is of a hooded, legless man doing the head shake. They filmed the actor waving his head around at 4fps, resulting in an incredibly fast and deeply disturbing motion when played back at the normal frame-rate of 24fps. The imagery was inspired by Witkin's 1976 photograph "Man With No Legs◊".
- The Austrian psychological thriller Goodnight Mommy has a Nightmare Sequence wherein Elias' mother strips down in the woods and starts spasming uncontrollably.
- In House on Haunted Hill (1999), one of the characters experiences a rather freaky nightmare while trapped in a sensory deprivation chamber. This starts with a ghost nurse "diagnosing" him, before asking the ghost of Dr. Vanacut for his "opinion". The Doctor responds by shaking his head in a blurry fashion.
- In Avengers: Infinity War, Doctor Strange is doing this as he's having spams from seeing millions of possible futures through the Eye of Agamotto.
- Innerspace combines this with Shapeshifter Swan Song when Jack (disguised as the Cowboy) loses control over his shapeshifting ability and undergoes an eerie facial deformation process wherein his head shakes uncontrollably.
- In What We Do in the Shadows, Nick does this in his bed as part of his transformation into a vampire.
- Happens quite a bit in Tetsuo: The Iron Man alongside some truly psychotic stop-motion sequences.
- An example that's Played for Laughs in Ultraman Zearth, when Katsuto — Zearth's human form — needs to transform, by brushing his teeth non-stop for 10 seconds. The results are as hilarious as it sounds.
- A Haunting At Silver Falls: After leading Jordan down to a convenience store with a TV, Holly begins to shriek, point, and move her head around rapidly. Jordan then discovers that the TV is talking about Wyatt Dahl, who is being put to death that night for murdering the twins.
- Buffy the Vampire Slayer: In the episode "Beauty and the Beasts", Pete does this while Hulking Out, shaking his head wildly and showing Tainted Veins.
- Doctor Who:
- In the TV movie, the Master attempts to steal the Doctor's body. As part of the process, his head shakes and blurs.
- "The End of Time": The Master uses the Immortality Gate to unleash a World-Wrecking Wave that transforms every human being into a copy of him, which causes their heads to shake at blurring speed while they're being converted.
- In the Farscape episode "Thanks For Sharing", the shapeshifting Corlata mercenary does this as it changes back into its Shapeshifter Default Form.
- Happens in Hannibal episode "Tome-wan". During his Mushroom Samba sequence, Mason Verger envisions Hannibal shaking his head this way for a few seconds until it changes into a boar head. Watch the sequence here.
- In The Immortal 2000, demons tended to do this in the time between the hero stabbing them and them being sucked into a spontaneous portal to hell.
- In season one of Misfits Simon does this when turning invisible.
- In the cold open of the Wire in the Blood episode "Torment" (Series 4 Episode) this happens with a mental hospital orderly to indicate the insanity of the viewpoint character, Derek Tyler.
- The Silent Hill franchise, heavily influenced by Jacob's Ladder, is the Trope Codifier, providing examples of head twitching as well as Marionette Motion all throughout the game series in random scenes and encounters:
- A non-demonic example is seen Metal Gear Solid. Gray Fox's exoskeleton and medicine, while enhancing his potential, leads him to have very painful spasms, complete with violently uncontrollable headshakes.
- Even scarier on the original PlayStation version as the head is shaking too fast for the framerate that the red glow emitted from the central eye can't even follow properly.
- Dawn of War: One Idle Animation for Chaos Space Marines and Khornate Berserkers has their head start shaking uncontrollably.
- Ultimate Custom Night: Withered Chica's Jump Scare animation has her shaking her head and flapping her arms violently.
- In Dead Space, Twitchers sometimes have this effect thanks to their Super Speed.
- In Overwatch cutscenes, Sigma suffers from this trope as his personality fractures due to a close encounter with a black hole. It never comes up in-game due to his mastery of his new gravity powers, but he hasn't managed to elimate the twitching entirely.
- In Emperor: Battle for Dune the shapeshifting effect of the Tleilaxu face-dancers is achieved this way. While the Tleilaxu are not demonic, they are still one of the most malevolent factions in the story.