Visible crew/equipment: When Maggie is in the pharmacy looking for abortion pills and is attacked, the camera cuts to Glenn twice before he rips the shelf from the wall to save her. The first time, behind him you can see that the glass next to the storefront door is empty. In the second cut, you can see someone standing on the steps. It looks like Melissa McBride. (00:25:20 - 00:26:00)
Pretty Much Dead Already - S2-E7
Visible crew/equipment: When Lori is cutting carrots and Shane is walking up to talk to her, look in the background behind Shane as he squats down. There is a person walking towards the barn.
Answer: Walkers are attracted to noise, they can tell who's dead and who isn't dead, in S1 when Rick and Glenn cover themselves in walkers' guts they're able to get far by walking through the herd of walkers because they smell like they're dead, but as soon as the guts get washed off by the rain the walkers immediately attack them, if you draw attention to yourself they will attack you which we've seen that many times throughout the series that it's not always successful. Whether you're covered in guts hiding under dead corpses or under a car.