I know that The Possession Of Joel Delany (1972) is often cited as a possible cinematic influence on Friedkin's The Exorcist (1973), but I had never seen this little gem until recently. The finale has little Johnny Whitaker (yes, from Family Affair) possessed by a "devil" yelling weird demonic gibberish in a surprisingly creepy and effective vocal track and attacking his mother (Sandy Dennis) as objects fly around the room. The devil is driven out by the chanting words of love from mom. It's a brief scene that might elicit giggles from some, but it's strange how similar some scenes in The Exorcist would play out nearly two years later.