When Michael takes the Valium he lifts his bottle to his mouth with his left hand but lowers it with his right.
Michael goes to the Midnight Mass and does not genuflect when he enters the pew.
During the bar scene, "Good Lovin' Ain't Easy to Come By" sung by Marvin Gaye and Tammi Terrell is playing on the soundtrack. Although the film is set in June 1968, the single did not come out until January 1969. The song was also used in the same scene in William Friedkin's 1970 feature film.
When Larry leaves the bar and joins Hank on the sidewalk, a 1970 Ford LTD sedan is parallel parked across the street. The earliest time frame that this model year would have been available was in September of 1969.
The phone in the living room is a model 1A2 with buttons for multiple lines. It had at least two lines based on the action in the film. It is shown with a standard line cord when this type of phone should have a thicker cord to handle the multiple lines, the lighted buttons and the hold button.
The telephone in the bedroom has a modular connection on the handset and a flat cord which weren't introduced until the mid 1970s. It should have a thicker hard wired cord like the kitchen and living room phones.
Jim Parsons mispronounces the name of the church as St. Mala kee.... It's St. Mala ki to rhyme with EYE.