The appearance of the Red Mona was initially inspired by the Phantom in "The Phantom of the Opera"
The shots speeding towards Finton as he suffers an anxiety attack within the hospital are inspired by the demon POV shots found in the Evil Dead films.
In the classroom scene, Danny says a line extremely reminiscent and in direct reference to that spoken by Sheriff Brackett in John Carpenter's HALLOWEEN.
The pumpkin which Nathan finds in a room of the abandoned hospital wasn't a prop intended to be on set by production. But in finding it they adapted the script and a subsequent earlier scene to incorporate the gag (and the pumpkin) into the film. Happy Halloween.