Creepiest Movie Children - Rotten Tomatoes
The Exorcist (1973)

Pre-teen Regan MacNeil is an adorable little girl, which makes her transformation into a spider-walking demon child even more disturbing. "Creepy" is hardly descriptive enough for a girl so thoroughly possessed she can rotate her head 360 degrees and sexually assault herself with a crucifix. Note to medical professionals: if your patient experiences levitation, projectile vomiting, and increased profanity, it's not puberty.