When they are covering Rick and Glenn with guts, Rick hands T-Dog the key to the Merle's hand cuffs. But when everyone runs back upstairs to watch Rick and Glenn in the street, T-Dog is still on the roof with Merle from before, trying to contact the others on the talkie, showing that he has the key.
When Rick and Glenn go after the truck, there is a thunderstorm with rain. Just after it ends the streets are bone dry.
When Morales is handed the axe and begins chopping the body, his face guard falls off on the first chop. It is then on again in the next scene and falls off again on the second chop. Then is on again in the next scene.
When Glenn and Rick are covering themselves in the guts of the walker, Glenn's coat is almost completed covered, except the arms and a bit at the bottom when Andrea gives him the gun. But in the next cut, when Rick begins chomping the corpse again, Glenn is only half covered.
At 37 minutes in, Rick takes a box van from a construction site to rescue the others trapped in the store. While backing up Rick looks over his right shoulder like he is looking out the rear window. The rear roll-up door is shown to be closed, all he could see is the interior of the box.
When Rick hot wire starts the 2010 Dodge Challenger he is pictured using a screwdriver to start the ignition. That model challenger and all new model Challengers use push button start, and also use a Key Fob system that makes the vehicle anti-theft. Without the key fob present and the fact they triggered the vehicle alarm would automatically disable the vehicles fuel delivery system making the vehicle inoperable.
Glen is using a CB radio to communicate with Rick using a military radio. This is not possible since CB and military radios use different frequency ranges.
The AN/VRC-12 radio in the tank has a CB handset attached.
Glen's CB radio is not plugged into any power, nor does it have an antenna.
When Merle is on the roof shooting at walkers on the street he fires a total of seven shots. The rifle he is using is a Winchester Model 70, .30-06 Springfield. This model of rifle only has a magazine capacity of five rounds.
When Rick and the rest of the group are stuck inside the department store they cover themselves with "guts" because the zombies can smell the living. However, in the second season when they are stuck on the freeway, zombies walk right by them while they are hiding under the cars. This is not a goof. In "Guts" when Rick and Glenn cover themselves, they do it to avoid being attacked once seen by walkers. In "What Lies Ahead", when the group hides under the cars, the walkers don't smell them because walkers can't smell any better than the living.
Using arrows to kill zombies, wipe them off and use them for hunting, causing contamination which they are so careful about at other times. However, there's no reason to believe they use the exact same arrows for both purposes.
When Sheriff Grimes picks up the M67 fragmentation grenade in the tank, it has a noticeably blue safety lever. This indicates it is simply a poorly repainted inert M69 training grenade, which are completely blue. An actual M67 is entirely green, with yellow factory markings stenciled on the body.
Each group has a different word for the "Zombies". Glen's group called them "Geeks". However, when Glen is helping Rick out of the tank, he referred to them once as "Walkers". He then reverts back to calling them, "Geeks" until Rick calls them "Walkers" which is the term Morgan used.
Food should be abundant. Canned food, dried goods last for years. Most people dying leaving food in their homes.
When Rick and Glenn get to the truck in the construction site they're forced to reverse from a horde of "walkers." Rick looks behind him to back up even though the truck has no rear window. He would have had to look in his side mirrors to see behind them.
When handing T-dog the handcuff key, Rick Grimes clearly gets blood on his hand after taking the glove off.