(at around 1h 16 mins) When The Narrator is quitting his job, the thermostat alternates between white and black as the shot cuts back and forth between him and his boss. (The 2009 Blu-ray release digitally alters the scene so the thermostat is now consistently white.)
(at around 1h 12 mins) When Lou is punching Tyler, Lou punches once and there is blood, it shows Tyler again and there is no blood, and then blood again when he gets punched the second time.
(at around 2h 5 mins) When The Narrator is breaking into the building (near the end of the movie), he slams a bench into the glass door, and its rebound hits him. He eventually shoots the door he tried ramming, and when he kicks the glass and goes through, the bench is gone.
(at around 2h) When The Narrator is in the police interrogation room at the end of the movie with the detectives, the sweat on the neck of his shirt changes from shot to shot.
(at around 47 mins) When Tyler's phone rings (with Marla on the other end), the camera pans towards the phone, showing a white paint spill on the left side. However when The Narrator walks towards it and picks it up, the paint spill is now on the right side of the phone.
(at around 22 mins) When Tyler is discussing the reason oxygen masks are on airplanes he is incorrect. Breathing 100% oxygen does not create a state of euphoria. In a loss of cabin pressurization, it is hypoxia (lack of oxygen) that can induce euphoria. However, Tyler never states as a fact that oxygen produces euphoria, it is simply his interpretation of the safety notices, and his explanation for why the people in the pictures have such calm expressions.
(at around 32 mins) When Tyler is editing the reel in the projection room he doesn't edit the sound in the reel he edits only the frame, but later on we can clearly hear the sound.
(at around 48 mins) When Marla is on the phone with The Narrator and exclaims that she has attempted suicide by a Xanax overdose, the camera zooms in on the prescription bottle clearly labeled "Xanax 300mg". Xanax is only sold as 0.25mg, 0.5mg, 1mg and 2mg tablets. The 300mg dose does not exist. Also, the pill spilling out of the bottle is 0.5mg pill.
(at around 2h 15 mins) At the end of the movie when the buildings detonate, the city block, or more so a localized city, would have caused the plate glass where the characters were standing on the floor of the adjacent building, to rumble or even crack or shatter, followed by a massive churning wall of dust to slam against the windows.
(at around 2h 15 mins) When the buildings detonated at the end they fell too fast, did not generate enough dust and did not rattle the windows and tremor the floor to the adjacent building where the characters were watching.
(at around 1h 9 mins) Even though Rule 6 is No shirts, no shoes, Bob (Meat Loaf) fights with a shirt on. But despite one of the eight rules being you are not allowed to wear shirts or shoes during fights was because Meat Loaf's fat suit had to be covered during these scenes. Within the film, it's possible the other members were repulsed by Bob's 'bitch tits' and made an exception for him.
(at around 1h 21 mins) When Tyler is cutting out various news clippings about the exploits of Fight Club/Project Mayhem none of the articles relate in any way to the headlines.
(at around 1h 35 mins) After the scene in the bathroom where Tyler threatens the police chief, as the waiters are emerging into the parking lot, you see Bob's (Meat Loaf) pants fall down, briefly revealing the body suit he was wearing.
(at around 2h 5 mins) During the fight scene in the garage between Tyler and The Narrator, the concrete wall moves when The Narrator is thrown against it.
(at around 27 mins) When The Narrator calls Tyler, the last 3 digits he presses are 135. But at the back of the card he's holding, the number reads 555-0178.
(at around 1h 15 mins) When The Mechanic (Holt McCallany) sprays the Seminary Student (Matt Winston) with a hose, the camera briefly shakes because the cameraman was laughing uncontrollably.
(at around 2h) When The Narrator is getting off the table in the police station after getting the gun, the wireless mic pack is visible and connected to his underpants.
(at around 2h 9mins) When the narrator is thrown down the stairs by Tyler Durden,You can see the stuntman's face falling down the stairs.
(at around 2h) When The Narrator is being held down on the table at the police station, a boom mic is clearly visible at the top of the screen for a few seconds.
(at around 34 mins) When Tyler is urinating in the soup, the boom microphone becomes visible as it moves to allow him to talk into it. *This has been corrected for the DVD.)
(at around 6 mins) When The Narrator talks to his doctor, the x-ray on the wall behind him is not only back-to-front, but also upside-down.
In Project Mayhem there is no names, but Bob gets called Bob four times. Twice by Tyler as a waiter and twice by one of the Space Monkey's when he is shot lying on the table.
(at around 8 mins) Bob mispronounces the steroids Dianabol and Winstrol as "Diabanol" and "Wisterol," respectively.