Effects Supervisor/Director/Producer Greg Nicotero is a direct disciple of the late George Romero, and the show CLAIMED to follow "Romero's Rules," but there is one glaring exception:
In seasons 3 and 4, characters wasted endless time stabbing walkers through the prison fence, instead of building flamethrowers. After being chased from the prison, Carol and Ty were attacked by burned, blackened zombies.
This is in direct conflict with "Romero's Rules," going back to Romero's original 1968 film. In NotLD, George Kosana's Sheriff McClellan advises a TV audience, "Just get yourself a club or a torch. Beat 'em or burn 'em, they go up pretty easy." It is one of the most iconic moments of the film.
In seasons 3 and 4, characters wasted endless time stabbing walkers through the prison fence, instead of building flamethrowers. After being chased from the prison, Carol and Ty were attacked by burned, blackened zombies.
This is in direct conflict with "Romero's Rules," going back to Romero's original 1968 film. In NotLD, George Kosana's Sheriff McClellan advises a TV audience, "Just get yourself a club or a torch. Beat 'em or burn 'em, they go up pretty easy." It is one of the most iconic moments of the film.
When they pick up Glenn's body for a brief moment you can see his head is fully intact.
The fuel they are using in their vehicles if it was an ethanol blend, would have degraded significantly in just 12 months, and this show takes place over a number of years, by which time the fuel would be unusable, and yet they seem to be using it without issue.
Daryl continues to ride a motorcycle, despite the fact that something that loud would draw the attention of both walkers and the living.
Throughout the series, characters regularly start and drive abandoned cars. In real life, over the several years covered in the show, the gasoline in abandoned vehicles would have degraded significantly, with many of them being unusable.
Firearms shooting many more shots than they actually hold, clearly no time to reload.
Throughout the series, Rick many times fires his Colt Python using only one hand. The recoil on a Colt .357 is very powerful, and one would need an incredibly strong wrist to be able to fire it with one hand and hit a long distance target.
Throughout the series it is clearly stated that everybody is already infected and will eventually turn into a walker, no matter the cause of death. People die from a walker-bite or have a limb amputated to stop the infection from spreading and hence survive. If the infection is already in everybody, a walker-bite would not change anything and do no harm beside the damage to the tissue itself.
Time for people to change to zombies varies greatly depending on the story line needs. The times people state it requires changes often and then does not match the actual times. It was stated throughout the series that the survivors didn't understand why the time to change varied. Some people turned almost immediately while some could go hours before it happened. The only consistency was that everyone would change.
Packaged foods have a shelf life ranging from 1 to 5 years. The zombie apocalypse began in 2010. Few if any food factories will operate, yet in the tenth season, a text appears that says, "After 15 Years," and they are eating packaged food.
Throughout the series the sound effect of a gun being cocked is used incorrectly. Often when a character draws a pistol the sound of a hammer being cocked is heard, but often the gun being used does not have an external hammer, but a internal hammer known as a striker plate (like a Glock). Or even with guns that have external hammers, like revolvers, we hear them being cocked but when we see the gun the hammer is still clearly uncocked.
Survivors would not run out of small arms ammunition for generations. The BATFE estimates between 300 to 400 billion rounds, that is around one third of a trillion rounds, of small arms ammunition in US in civilian hands, retail and wholesale pipelines, law enforcement and military (in that order). Even if if 1/3 were shot in initial zombie world and 1/3 were destroyed or never found, there would still be millions and millions of rounds of ammunition -- per survivor -- available. Contact weapons might be wise for dealing with most zombies due to noise, but everyone would be always carrying and using firearms to deter other humans and use as last ditch against unexpected large numbers of zombies.
A lot of the time characters kill walkers by pushing a knife up through their bottom jaw. Most of the knifes they use are not long enough to reach the brain and so walkers are essentially just being stabbed in the mouth, yet this seems to be an effective method.
There is no clear reason why Michonne's technique of walking with two zombies on leashes deters other zombies from attacking her. By this logic, anyone walking around amongst the zombies, regardless of whether or not they are covered in zombie blood and guts, should be safe, so long as they don't do anything to draw attention to themselves.
Guns and ammunition even more so should be easy to find over with 300 million registered firearms, and millions of illegal and millions of military/law enforcement.
In the first season finale, it is clearly established that only the brain stem, at the base of the skull, reanimates. Yet, throughout the series, survivors stab the dead in the front of the head, which would have no effect whatsoever.
Throughout the series, Carl physically ages much faster than anyone else. Neither a baby (Judith) nor a boy (Sam Anderson) who would be the same age as Carl in the time frame, show such accelerated aging. Not only is there is no explanation, all the characters act oblivious to it. Despite Carl's slow brain development, he is still viewed as being much older.