After one of Kenny McCormick's deaths, he promptly attacked the morticians. Mis-diagnosed as a case of pinkeye, the entire town fell prey to the virus by Halloween night, including Pip, Wendy and Chef. Many were killed while zombified before it was revealed that only killing the head zombie would end the virus. After Kyle cut Kenny apart, everyone intact returned to normal.
They are not known to be related to the Nazi Zombies seen in South Park: The Stick of Truth.
- Pinkeye (s01e07)
The original zombies are one of the game's most prominent villains, with an entire challenge map dedicated to fighting them. The Pee-Tron tower works best against them.