Continuity mistake: When Daryl is driving the hospital van, it shows that he is going to land upside down, on the vehicle's roof, when he drives off the parking garage. In the next scene, the vehicle lands on its wheels, as if it has done a complete front flip. (00:30:00)
Continuity mistake: On the roof all the survivors are discussing their escape plan while T-Dog is lying down injured by Merle. In the next scene people are wearing rain coats and covering their bodies with the walker's remains as Rick proposed. T-Dog has taken off his cap and looks fine. Rick gives him the handcuff keys to free Merle. In the scene after, while Rick and Glenn went out the streets, the others go back on the roof to watch them from above. Nobody is wearing a raincoat and also T-Dog is in the same condition as before, lying down with his cap on. (00:24:00 - 00:31:15)
Continuity mistake: When Glenn wakes up in the prison you can see two chairs leaning against the walls behind him when he stands up. These are still present in the second shot, but when the camera moves back for the third shot they have mysteriously disappeared.
Continuity mistake: Glenn demands that Abraham stop the truck so he and Tara can get off, the two male characters then have a scuffle. We can see Eugene in the background standing next to the truck facing right of the camera. When the camera cuts back to Eugene by himself, he's now facing the opposite direction. Also the items in the back of the truck move from left to right. If you look carefully, you can see that the entire image was flipped horizontally.
Continuity mistake: After the part where Merle and Daryl save the people on The Bridge, Merle gets agitated at Daryl and grabs him and rips his shirt. On the left side of Daryl's back, he has tattoos on his right side, but as he walks away he suddenly has the tattoos on his left side. (00:25:50)
No Sanctuary - S5-E1
Continuity mistake: At the start of the episode when Tyreese and Carol are walking down the railroad tracks towards Terminus, they encounter a herd of walkers coming out of the woods. One of the first walkers to cross the tracks is a male walker wearing a burgundy sweatshirt with a rip in the middle. When gunfire erupts at Terminus, the walkers turn their attention towards it. In the next shot when they start to head towards the sound, we see the same male walker now in the middle of the herd yet to cross the tracks, next shot after that, we again see him at the front of the pack.
Continuity mistake: In the scene where Merle is the in big box late 80's chevy with big 20-22 inch rims he is shown driving it in the barn yard drinking, playing music, and zombies following him. The shot changes a few times within the same scene with the big rims on, in one shot the car is shown with him driving it but the stock rims (15") are on the car, the paint of the car looks a little darker too. Then the shot changes again while he is still driving it and the big rims are on the chevy again. The shot that shows the stock rims is a pretty fast shot so it could be easy to miss.
Too Far Gone - S4-E8
Continuity mistake: When Hershel crawls away and the fight begins, in the long shots of the governor's men Hershel's body can not be seen next to the cars, this is from all angles.
Pretty Much Dead Already - S2-E7
Continuity mistake: As the group kills the walkers that come out of the barn, the camera shows several different vantage points from in front of the barn, inside of the barn etc., it shows the walkers lying with a clear path between them, and in another it shows the walkers lying in a jumbled pile with no path between them. This goes back and forth a few times until Sophia comes out of the barn, and there is no clear path again.
Continuity mistake: When the Winnebago breaks down. Shane and T-Dog offer to drive ahead to check out what could possibly be a gas station. Shane tells Rick to hold the fort while they're gone. Meanwhile Rick is dealing with dying Jim. When discussing Jim's predicament, Shane is there, he hasn't gone anywhere. Then when they put Jim under the tree T-Dog is there too. Then they all drive off like the breakdown never happened. Nothing is mentioned about whether Shane and T-Dog found a gas station and if they did, it was very quickly sorted out - two minutes tops. (00:31:00)
Continuity mistake: When Rick, Carl, and Michonne are leaving King County (Rick's home), they must travel around a wreck involving two cars and an overturned RV. They drive along one side of the road. When the camera angle changes, they are on the opposite side of the road going the other way. (00:41:30)
Continuity mistake: When Mica and Lizzie are running from the walkers on the railroad tracks, they easily outrun them and gain several meters' distance in a few seconds. When they are running to the house, the walkers have suddenly caught up and are directly behind them.
When the Dead Come Knocking - S3-E7
Continuity mistake: The first shot of Maggie waiting for the Governor to enter shows her wearing a black tank top with her shoulders bare. After he cuts the duct tape around her wrists, the camera pans up and she now has black bra straps showing on her shoulders. (00:26:10)
Continuity mistake: When Glenn is with Tara and getting ready to move out, he puts on his helmet and you can see it is strapped on. When the shot changes, he swings the fence open and you can see his strap is lose. The camera angle changes again and the strap is back on again. (00:38:15)
Internment - S4-E5
Continuity mistake: When Rick gets out of his car and talks to Maggie inside the prison gates. The car door opens and shuts throughout the conversation.
Continuity mistake: In the flashback to the prison, Hershel says "we've been here two months." However, when they show Judith she is shown to be the same age she was when the prison fell (around 9-10 months) If they had only been there two months, and Lori delivered within the first week of being there, the baby should not be very old.
Chupacabra - S2-E5
Continuity mistake: During the scene where Norman Reedus is talking to Michael Rooker, watch the dirt and sand around Reedus' mouth appear and disappear during the talk while he is on his back.
Continuity mistake: In Season 2 episode 7, "Pretty Much Dead Already," at the end where Rick shoots the walker Sophia, she falls to her right. In the next episode, "Nebraska," picking up immediately after the last, she is in an entirely different position, as if she fell forward.
Continuity mistake: When Beth is looking for a key in Officer Dawn's office, she encounters Joan lying dead in the office from bleeding out, apparently from suicide with a pair of surgical scissors. Her left hand is covered in blood. But when Officer Gorman enters the room and Joan starts to turn into a walker, the blood on her hand has disappeared.
Answer: The walkers could have knocked them down more than once. There may have been another wave that knocked down the fence earlier and they're going to put it up again soon.
Captain Defenestrator