In the movies Poltergeist, The House on Haunted Hill, and Frankenstein, they used real dead bodies as props because fake ones didn't exist and would be too costly to make. – WTF Fun Facts
Source: https://www.cheatsheet.com/entertainment/the-poltergeist-yes-those-are-real-skeletons-terrorizing-jobeth-williams-in-the-pool-scene.html/














