When they open the basement door and the Tarman comes out, you can see smears on the wall and door where his arms have slid. When the group go into the basement afterward, there are no smears on the wall near the door.
When Frank is explaining how the original Night of the Living Dead is based on a true story, he states that the true story occurred in 1969. However Night of the Living Dead was released in 1968, a year before the incident happened. In the original script Frank said the event happened in 1966, but Dan O'Bannon changed the line because he felt it would be better if the character was unreliable.
(at around 46mins) When the two paramedics arrive on scene to examine Frank and Freddy, one asks the other about his stethoscope working because he could not find a blood pressure. The second paramedic has the same problem. However, neither are seen with the stethoscopes in their ears.
The radio dispatcher states "We have a 10-32 from E.M.S." "...Request a 10-51 Code 3..." The official Police 10-Codes defines a "10-32" code as a "Man with gun", a "10-51" code as "Wrecker needed" and a "Code 3" as "Emergency lights and siren". The Code 3 reference was the only correctly-used code.
When Frank locks the door to the freezer containing the frozen zombie, it has a white door. Later, when the door is opened by Freddie, after which Burt bludgeons the zombie with a red mining pick, the door is completely different, dark tarnished metal instead of painted white.
Clu Gulager's character name is spelled as 'Burt' in both the credits and on the 'eye test' poster in Frank and Freddy's office. However, the note on the door leading into the warehouse Office (which reads "No Cash in Safe After 5:00PM!") is signed by 'Bert'.
When Spider and Burt rush out of the embalming room toward the police cruiser, a character can twice be seen quickly looking out of the sliding peephole in the door. The second time, it is quite obvious that the person looking out is not Tina or Ernie who by now are the only two people left in the embalming room.
The skeleton woman who is chopped in half in the foyer of the morgue after being pulled though the barricade. As she is held in place by Spider on the floor we see a large prop, plywood or cardboard, fall and cover her completely. The shot cuts away very briefly. When it cuts back the prop has moved.
The punks open the cemetery gates when the entered the graveyard. They were still open when Tina goes to see Freddy and they were open when Chuck and Casie were being chased by zombies to the warehouse, and they were still open when Trash comes out as a Zombie, but when Burt and Spider are driving through the graveyard they crash through the closed gates.
After Frank and Freddie are gassed my the faulty barrel and wake up, Frank closes the barrel lid before they go upstairs. Later when Burt comes down to get the phone number from the barrel he closes the lid a second time.
When the movie shifts from the graveyard to the funeral home, it clearly states that the time is 9:20 on the screen. Yet when you look at the clock behind the dead body and Don Calfa (Ernie) the clock clearly shows the time is 10:20.
(at around 1h 12 mins) When Burt and Spider are in the cop car, and they screech on the brakes to avoid hitting a horde of Living Dead, the camera man can be seen in the back seat of the car, as well as the camera (look for a red light).
(at around 1h 5 mins) When the first two police officers arrive on the scene of the two disabled ambulances, a man with black curly hair is visible in the backseat of the cruiser (seen through the rear-view mirror).
(at around 1 hr 8 mins) At the moment when Ernie slaps Spider in the embalming room look to the left of Ernie. You can see just the head and back of someone under the embalming table who is mostly hidden by the sheet covering the end of the table. This person (puppeteer?) is most probably there to operate the half woman skeleton on top of the embalming table.
(at around 59 mins) When the zombies break in for the second time at the back store room, Scuz is attacked and killed by the half woman corpse. As Burt separates Scuz from the zombie, you can see a single black string coming from the zombie's head attached to the ceiling.
Although the titles and characters mention the setting as Louisville, Kentucky, the skyline of downtown L.A., including the much-photographed dome of City Hall, is clearly visible as the crew cruise toward the warehouse early on in the film.
The ash from the mortuary incinerator is implied to mix with the rain that is falling to make a zombie creating brew. Even though the amount of rain is shown to be a heavy downpour (several inches accumulate in the cemetery in a short amount of time) there is no way that the rain/ash mix could penetrate through six feet of soil and a coffin in the short time portrayed. Even heavy rains will penetrate no more than a few inches of soil. It takes months if not years for water to penetrate to lower layers of soil. This is even more the case given the soil type that is around the Louisville Ky region where the movie is supposed to take place.
Ernie claims that the process of rigor mortis begins in the brain. This is not true as rigor mortis only occurs in muscle tissue and the brain is not composed of muscle. Initial onset DOES begin in the head however specifically the muscles in the eyelids, jaw bone and neck.
Ernie tells Burt that the embalming business is not an exact science and is basically passed down by word of mouth. When in actuality embalming was practiced by the ancient Egyptians for centuries and modern embalming was perfected in the early 1900's, and has changed very little since.
When Punks break into the cemetery, it's locked and doesn't seem used for a long time, everything is in weeds, yet when the rain animates zombies all except one seem like they just died today and were all buried immediately!?
(at around 1 hr 6 mins) Dozens of zombies attack the paramedics in order to eat their brains. But when the cops show up, the zombies have disappeared and brains are literally pouring out of one paramedic's head. Were they not that hungry?
(at around 1 hr 13 mins) When Frank is going to cremate himself, he turns up the fire in the crematorium, and then climbs on the slate. He then pushes the slate inside the crematorium. He does not scream in pain from the burning flames which have been burning him for more than a few seconds, and he even hesitates slightly before reaching outside the door to press the button to lower it.
The skeleton that rises out of ground in the final before credits has a perfect pair of blue eyes in it's skull. The human eye soft tissue and liquid and would have rotted completely away if it had been the ground long enough to fully skeletonize.
(at around 1 hr 2 mins) Immediately after Trash emerges from the mud, the movie fades to a clip of rain with smoke rising. The clip is looping in forward and reverse, as you can see the rain and smoke rising and falling several times, pausing briefly between each cycle.
The goof items below may give away important plot points.
Crew or equipment visible
(at around 1 hr 22 mins) At the end of the film when the military orders the destruction of the city, if you look carefully after the explosion you can see a reflection and shadow of the buildings in the background. You can clearly tell it is a miniature.
Trash is attacked by the corpses and later animates. In later scenes, you can see there are no bite marks on her and her head is intact. Since she was still alive, why wouldn't they eat her brains? They had no problems with anyone else.
The entire premise of the ending is false: a nuclear explosion would completely sterilize the entire area, eradicating all organisms down to the cellular level. This would include all traces of the trioxin gas - there wouldn't even be enough to seed rainclouds, as is shown at the end.
(at around 44 mins) When the Tarman kills Suicide, you can see the real life teeth of the actor underneath wearing the mask. It's easiest to see when he pulls the sheet away and sees the Tarman standing there.