A well-crafted and visionary film is essentially a living entity with infinitely varying facets. For every single shot in a horror movie, there's a wealth of peripheral images to analyze - bizarre background action or creepy movie Easter eggs that are just waiting to be discovered.
Not all of the these Easter eggs are designed to be enigmatic, however. Some ostensibly "hidden" messages in movies are actually right there in plain sight. The legendary David Lynch, for example, is well known for his attention to detail, but as evinced by many bizarre behind-the-scenes Hollywood stories, even Disney has been known to dabble in bawdy subliminal imagery.
A particularly horrific moment in the film occurs while Diane Freeling blow dries her hair and is subsequently attacked. At the beginning of the scene, the photo collage on her dresser shows a photo of Carol Anne in the middle, but by the time the poltergeist enters the scene, the photo has changed to that of a demonic face.
When Janet Leigh appears in 1998's Halloween H20, she gives a whimsical nod to her most famous character, the ill-fated Marion Crane from Alfred Hitchcock's Psycho. Savvy viewers will note that the car Leigh arrives in the very same vehicle that Norman Bates encapsulates Marion in. Even the license plates are the same.
As it turns out, William Friedkin's 1973 masterpiece, The Exorcist, contains a lot more subliminal background images than most fans noticed. One such image appears during the penultimate scene in which Father Karras demands that the devil enter him. Just before he heroically throws himself out of Regan's bedroom window, Karras's mother's face appears in the glass.
When Sam Raimi paid homage to Wes Craven's The Hills Have Eyes in 1981's The Evil Dead (a poster for the former appeared on Ash's demonic cabin wall) the gesture did not go unreturned. Craven responded by including some footage from Raimi's 1984 masterpiece A Nightmare on Elm Street.
According to Cinema Blend, Raimi then nodded back by featuring Freddy Krueger's glove in Evil Dead II: Dead by Dawn.