They usually show no allegiance to any individual and will attack whoever, or whatever, stands in their path.
The Zombies are mindless monsters at first created by Dr. Madd, part of his Creations with only the Doctor himself having any semblance of control over them.
Zombies are cobbled together from pieces of every faction; Green, Tan, Grey, Blue, and even the Black and Red nations. During Army Men 2 they were assembled via a massive, complex molding machine that created Zombies at an extremely quick rate.
As they are sporting mismatched colors, and typically make loud groaning noises, they are usually easily identifiable. Their slow speed also makes them easy to dispatch, but in some cases, Zombies can have a high resistance to damage.
Zombies in History:
Army Men 2:
In Army Men II events, the Zombies are first encountered on Dr. Madd’s island. Before being destroyed, the molding machine that creates the Zombies is able to make a handful of incredibly resilient Zombies that can either be evaded or destroyed after prolonged, sustained fire on them. They later appear in Area X in a caged off area, and can be freed. Assuming Sarge and his men stay out of their way, they will attack nearby Tan soldiers. Interestingly, a computer located in the middle of the caged area seems to control the Zombies to a slight degree, as destroying the computer will instantly kill all the Zombies.
Army Men: Toys in Space:
In Army Men: Toys in Space events, Zombies only appear in some vague battle reports. This reports stated that once killed, some soldiers turned into Zombies and attack every faction. There are also reports that they could be controlled in some way by accident, but this is already very unlikely.
Army Men: Sarge’s Heroes 2:
Zombies appear in Dr. Madd’s Castle, after a long time without being seen. They were patrolling the labyrinthine yard, the graveyard and the inside of the castle.
On this occasion, inside the castle medical stretchers could be seen with pieces of soldiers being glued together: Half-assembled Zombies. Although some of these may have been made not just of plastic soldiers, but of action figures.
Areas currently infested by Zombies
There are zombie remnants in some areas of the Plastic World, as well as in the Real World. But none of them pose much of a threat to anyone. The only area more significant is old Greentown.
Shortly after Lord Malice’s attack on the peace treaty in Greentown, in 2004, there was a zombie infestation that caused the Green Army to have to close the city and quarantine it. Currently no one can enter, and no one can leave it.
The Green Army did not want to bomb the city because of its historical and architectural value. For now it remains closed until some initiative is taken, which makes no sense since the situation does not generate problems as it is.
Sources for this article:
https://armymen.fandom.com/wiki/Zombie
https://armymen.fandom.com/wiki/Dr._Madd%27s_Creations