I figured it was either Michonne and Andrea or one of the Gov's scouting parties... However, Merle seems like a likely choice, looking back at the preview that showed him, the background is right for him to be standing over Carol in that shot.

Damn, just when Carol was getting some depth.

Being a hardcore zombie survival nut, I found myself screaming at the tv more than not the first two seasons, and attempting to explain to people that in a real deal situation, the choices made by these people would have had them all dead long ago, but the choices have to be stupid for drama purposes.

Then I realized after the first two episodes this season, when I was starting to feel like giving up on it, what with Rick and crew not taking out the prisoners leader and forcing the rest to fall in line right off and all.

Then I realized, all those sheep watching this show will think they're so prepared to surive a zombie apoc, only to make their choices based on what Rick did, instead of common survivial instincts... They won't be around long, which means more resources for us! So now I've done a 180, I actually want them to be stupid on the show. ;p

Besides, we all know the real threat in such a world wouldn't be from the dead, they have predictable routines and after a month or so, will be no sweat (minus roaming hordes) No, the real threat comes from other survivors.