When Charlie is getting an enema from Judy, he's on his right side. Enemas are typically given with the patient laying on their left side as this is thought to anatomically facilitate passage. Western hemisphere storytelling theories suggests that visual imagery is read from left to right. This may have brought the filmmakers to put Charlies face "first" and bottom "last" to put draw larger focus towards the human interaction rather than the procedure.
When Charles 'Charlie' Mayeaux is smoking a cigarette he puffs and exhales as if he drew smoke in, yet the cigarette isn't lit and when he exhaled, no smoke either.
Cameraman's shadow on the floor in front of Charlie's bathroom stall just as the camera begins to rise over the top of the door.