Whilst the zombified Shane was nothing special in terms of physical appearance, it was vitally important in changing the world of the survivors, as it proved that everybody turned, whether bitten or not. After a confrontation between the two, Rick is forced to kill Shane, and is waiting to test the reanimation theory when Carl appears to pull a gun on him. Of course, Carl instead shoots the Walker-Shane, meaning that not only had he caused major disruption to the group, but he also became Carl's first kill.
12. Gas Mask Zombie
The group's arrival at the prison provided a whole new playground of previously unimagined walker forms, and one of the most horrendous to behold was the gas mask walker. After shambling towards Rick, he is brought to the ground and has the mask ripped from its face. Well, that's not exactly true, it has its mask AND face ripped from its head, causing even Rick to pause for a moment to keep his breakfast in place. But like several kills before it, the gas mask walker signifies a tougher attitude, as Rick regains his senses extremely quickly, viciously stabbing the thing in the face.
