There are different types of zombies. some more dangerous than the others. Some do different do things to attack you or your partner.
Common Zombie- This zombie could be Nazi, Imperial, Soviet, or American zombies depending on the map. These were soldiers in WWII, Soviet scientists and Asian civilians who dies and then was reanimated by Element 115. They appear every round except hellhound rounds in the small rounds, or space monkeys. They appear in every map.
Hellhounds- These species came known to be when Samantha's dog, Fluffy, was impregnated and her father and Edward Richtofen tested Fluffy in the MDT. This result was unsuccessful, turning Fluffy, as well as her new babies, into hellhounds. These hellhounds come every 4-7 rounds. They appear in Shi No Numa, Der Riese, Kino Der Toten and No Mans Land on the map Moon.
Crawler Zombies-These were already zombies that were tested with Nova 6. Whenever the player kills the crawler zombies, they will create a mini explosion of Nova Gas, and any zombies within the explosion will die. They appear usually when you are in the power room or when you turn on the power. They appear in the maps Kino Der Toten, "Five", and in Moon as Phasing Zombies (see Phasing Zombies).
Pentagon Thief- This is not technically a zombie. He was a dead human that had not turned into a zombie and was infused with Element 115. He comes every 4-6 rounds after turning on the power and comes to steal your weapon. If you kill him before he takes your weapon he drops a Bonfire Sale and Max Ammo. If you kill him after he takes your weapon, then he drops a Fire Sale and Max Ammo. If you don’t kill him or you kill him when Insta Kill is present, then he will only drop Max Ammo. He only appears in "Five".
Space Monkeys- These were monkeys that were sent into space but turned into zombies by Element 115. These monkeys either try to hurt you or take away your Perk-a-Cola. They do this by running to you Perk-a-Cola Machine and start banging and breaking it. If they succeed, you lose your Perk-a-Cola, but if you kill all of them before they touch your Perk-a-Cola Machine, then they drop a Perk-a-Cola Power Up and Max Ammo. They only appear in Ascension.
George A. Romero- He was a director shooting a new movie called Call of the Dead, when a zombie snatched him up and infected him halfway. He is half zombie and half human almost like the Pentagon thief, but has about 4x-5x more the health. He will use a movie studio light to attack you. If he hits you will be shocked by lighting and temporarily blinded. If any zombies touch him, they will be electric zombies and become more dangerous. He only appears in Call of the Dead.
Napalm Zombie- These zombies are in fire and walk around. These zombies will take your health down if you just get by him. If a player kills the zombie, it will explode killing any zombies near it. Then it creates a wall of fire that if zombies or player(s) go through it, they will get downed/die. They appear only in Shangri La.
Shrieker Zombie- These zombies sprint to you at full speed, even faster than a players sprint and shriek at you trying to get you downed. They appear only in Shangri La.
Zombie Monkeys- Are monkeys that are also infected. They try to take power-ups that zombies drop. They appear only in Shangri La.
Astronaut Zombie- This is a zombie that is an astronaut and walks slow. It has a name of one of your or another players friends, but not one of the people playing. If you get to close to it, it picks you up and head-butts you. When it does this, your life is down to 1, if you had a perk-a-cola, then you lose one of them, and you get teleported to a part of the map that you have bought (not No Mans Land). When you kill him, he explodes, but it does not hurt you. It instead hurls you up in the air. They appear only in Moon.
Phasing Zombies-These species of zombies are adapted forms of the crawler zombie. Unlike the crawler zombies, the have the ability to phase, or teleport. They only appear in Moon.