Revealing mistake: Near the end of the show, while Rick is still in Atlanta (he is on a secondary paced road), you can see vehicular traffic moving on a bridge in the background.
Continuity mistake: After they steal the car with the alarm blaring, there is a shot of the white van turning left down a road. It has just rained but the road is bone dry. A shot later there is water on the road.
Continuity mistake: After Rick and Glenn cover themselves with guts, Rick tosses T-Dog the handcuff keys for Merle. T-Dog is at that moment in the rain coat and has on no hat, standing and appearing OK. The group then rushes up to the roof to watch Rick and Glenn on the street, and tell T-Dog to get back on the CB radio. Suddenly T-Dog is now leaned back sitting against the wall on the roof again with his hat and regular clothes acting all beat up again, and then shows Merle he has The Key.
Visible crew/equipment: When Rick hugs his family, a crew member can be seen filming over the red car. (00:10:40)
Continuity mistake: As the scene opens on the rooftop with Daryl, T-Dog, Rick, and Glenn observing the area that Merle had been handcuffed to the pipe, blood splatter magically appears around the severed hand when it wasn't there at the end of the previous episode. (00:05:10)
Audio problem: In the scene when Andrea is mourning the death of her sister, Rick walks up to "tell her how it is." Andrea points a gun at Rick with just her right hand. When the gun is coming up to Rick we hear the slide being cocked, this can only be done with two hands. (00:03:35)
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)
Factual error: The microscope in the CDC lacks objective lenses. (00:36:27)
Factual error: One of the machine guns set up to defend the CDC in Atlanta is a Soviet DShK machine gun. This weapon would not be in use by American troops in an American city.
Factual error: At CDC headquarters, Dr. Jenner shows Rick and the group an MRI of an infected patient's brain activity as they die and subsequently resurrect. The patient is shot at point-blank range as the barrel of the gun can be seen in the MRI. This is impossible. MRI machines are highly magnetic and the gun would have been ripped from Dr. Jenner's hands with such force that not only would he not have been able to shoot, the MRI machine would have been destroyed.
Continuity mistake: At the end of the previous episode, the sun was setting but wasn't set fully yet. There was still a decent amount of light left outside as the door to the CDC was opened. At the start of this episode, as they are entering, it's already pitch black outside.
Continuity mistake: When the walkers come through the cars, most shots show Carl and Sophia to be under the same car. When Sophia is attacked by the walker, Carl is not there and Sophia is shown on her own in other shots as well. (00:19:25 - 00:20:05)
Suggested correction: They never get under the same car. When we see them first get under the cars, they are both seen getting under cars going in the same direction at the same time (they'd have to go in opposite direction to get under the same car from both sides). Then in the first close up of Sophia, we can see Carl's head in the shadow and then a strip of sunlight indicating 2 separate cars.
Revealing mistake: When Carl rolls out the knife pack he found, the scene cuts to Shane working on the engine, and you can see traffic on a highway through the bottom of the windshield. (00:33:00 - 00:34:00)
Other mistake: When Daryl is cutting open a walker in the woods to see what meat it ate while searching for Sophia he stabs the walker several times, but the knife is not bloody and it stays clean. (00:33:30)
Continuity mistake: When Carl gets shot, and we see him in the ground, not only does the blood spot on his short change in the next shot of him on the ground, but he's in a completely different shirt. It's still a cameo shirt, but the cameo pattern is different.
Bloodletting - S2-E2
Continuity mistake: When T-Dog is telling Dale that all he found was ibuprofen and cigarettes, he is holding his hand up and they are both looking at each other. In the next shot, suddenly his arm is down and they are both looking forward. (00:22:44)
Chupacabra - S2-E5
Continuity mistake: Daryl ripped off his shirt to wrap around his wound, and was left in only his vest. Except, a shot later, he's seen wearing his shirt again, cutting off the walker's ears. (00:25:30)