NPC stands for Non-Player Character or Non-Playable Character. Thus an NPC zombie is a zombie that is not controlled by players, but a computer running the game. For a long time, there were no other types of zombies in Brawl Busters. However, after the introduction of the Zombie Infection game mode, there are also PC zombies (PC stands for Player Character or Playable Character) that are controlled by players. The group of NPC zombies and the group of PC zombies are distinct, that is, every type of zombie is either a NPC type or a PC type, but not both. However, for each PC zombie there is a NPC zombie that is very similar by looks and somewhat similar by moves.
No game mode has both NPC zombies and PC zombies; NPC zombies are only found in the Zombie Survival and Boss Battle game modes, while PC zombies are only found in Zombie Infection. Currently there are 15 different types of NPC zombies: Striker, Jailhouse, Viral, Rookie Treat, Minor Treat, Major Treat, Rookie Crash, Minor Crash, Major Crash, Lugnut, Bones, Skull, Little Leaguer, Flatfoot and Skull Rock. Some of these zombie types are very similar to each other by looks, behavior and/or the maximum health.