Corrected entry: As Regan pukes on Father Karras the superimposed vomit passes right through her teeth twice.
Correction: It was a practical effect done by running a tube into, and then back out of, Linda Blair's mouth. There was no superimposition, therefore this mistake cannot be correct.
Corrected entry: In the "Party Scene", Fr. Dyer tells Chris about the death of Fr. Karras's mother after Chris inquires about Fr. Karras. A few scenes later, when Fr. Karras first visits "Regan", she speaks to him about his mother. As he leaves the house he asks Chris if either she or Regan had knowledge of his mother's death and Chris says "No". Chris's answer to Fr. Karras helps the validity of the demonic theory, but doesn't match what took place previously in the movie (DVD).
Correction: Chris doesn't say neither of them knew of Karras' mother's death - she tells Karras she knew, but Regan did not, which matches up perfectly with the earlier scene.
Corrected entry: In the final scene, Regan's house has disappeared, in one shot, as the priest stands at the top of the stairs and looks at it.
Correction: If you visit this location in Georgetown, you will see that the house is actually very far away from the stairwell.
Corrected entry: When Regan makes the room shake, the door and walls start cracking. Later in another scene the door is perfectly fine, with no crack in it.
Correction: Earlier in the movie, we see that Regan's room has two doors, next to each other, the other one is probably leads to the closet. After they have been shaken by Regan's demonic force, in a scene a few minutes later, during the exorcism, we see a shot of both doors where one of them are cracked.
Corrected entry: The movie establishes it's own rules regarding the reality of the physical abuse suffered by the Regan character. Apparently, all the evil manifestations and physical damage sufferd by Regan is real, for she has the scars at the end of the movie to show it. This shows that they are not just a mental trick played on the others by the 'demon'. So when Regan turns her head completely around at two different points in the movie, the actual physical damage she sufferd should have killed her. You could even hear bones cracking during the sequence, suggesting that she was indeed going through some extreme physical suffering. Even if the 'demon' kept her body 'alive' with his special powers even though it should have been dead, Regan should have died moments after the 'demon' left her body and invaded Father Karras'.
Correction: Not exactly. Job 1:12 says "And the Lord said unto Satan, Behold, all that he hath is in thy power; only upon himself put not forth thine hand". This is usually interpreted that the Devil (or demons) can not kill humans, even though they may tempt us, or wreak havoc with our lives (although they may make other humans kill us - bit of a loophole there). So Pazuzu had to keep her alive during any potentially lethal damage, such as the head-twist, and heal her back after it was done. The other injuries were superficial, and keeping them would increase the "fun" Pazuzu had with the family. And besides, Pazuzu would want to keep Regan alive in pure self-interest. He knows there are times he may have relinquish control of the body for a while, and would not want to come back to a broken "toy".
Corrected entry: The bridge scene. Chris McNeil must have arranged to meet father Karras on the bridge. He walks up behind her, stops, and then says: "Mrs. McNeil?" She tells him to go away. He replies: "I should have told you I wouldn't be in uniform." There was no sign of her recognising him. But the film indicates that she must have seen him on several occasions and would have known who he was. Early on in the film she sees him talking to a younger priest and watches them for a few seconds. At the party she asks Father Dyer: "Who is the priest I keep seeing?" Father Dyer tells her that the priest is called Damian Karras and that he is a psychologist. Therefore she should have recognised him.
Correction: When Father Karras says, "Mrs. McNeil?" she doesn't look at him, she simply says, "Please go away," probably thinking he was just a fan. It isn't until he says, "I'm Father Karras," that she looks at him.
Corrected entry: When the priests are doing an exorcism on Reagan she floats above the bed and breaks the restraints that the doctors put on her from hurting anyone and herself. Then when she comes back down Father Karras rips a rope off the headboard and ties her hands together. Then she sits up and hits him in the back of the head. Later when Karras comes back in the room, as the other priest is in the bathroom, her hands are tied back to the bed in the restraints that she broke when she floated off the bed.
Correction: If you'll remember, right after Father Karras gets up from the floor (after being hit by Reagan), Father Merrin tells him that they should go outside and get some rest before continuing with the exorcism. At this point, Merrin leaves the room, and Karras sits on the bed right next Reagan. He stays there for a couple of minutes, turns his head towards her and then we cut to the scene outside of Reagan's room with both priests sitting in the hallway. Karras could have tied Reagan to the bed during the moments when he they were alone, right before joining Merrin outside.
Corrected entry: When Father Damien first sprinkled tap water onto Regan, she was screaming as she was in pain. Later in the movie, Father Merrin sprinkled holy water onto Regan and that burned her as well. Wouldn't tap water, which was not blessed, have no effect at all compared to holy water?
Correction: Because she screamed in pain when splashed with tap water (after being told it was holy water), Father Damien had a hard time proving that Regan was actually possessed to the other priests and bishops. Simply put, her first screams were a plot point to make things difficult for Father Damien, and not a mistake.
Corrected entry: In the recent re-release of the Exorcist, in the scene with Linda Blair's character tied up and spouting expletives, there is a cut to her character standing arms raised in a silhouetted black lit pose. Then it cuts back to her being bound to the bed.
Correction: The figure wasn't actually her, it was just a vision, since the devil is also standing next to her.