Basically they are the walking dead. They will chase and turn any human into a zombie. Zombies can also use the chainsaw very well.
A zombie will be created if you electrocute a corpse.
Zombies like brains ; they eat them and won't attack Maxwell if he holds one. They will also eat hearts and any other organs or flesh parts you summon. They will even eat babies.
Zombies will be lit on fire when they get too close to a fire source and will be destroyed shortly afterwards. Large groups of zombies can also be quite easily killed by using a lawn mower, this being a reference to Plants vs. Zombies.
NPCs that are attacked by Zombies become Zombies.
You can use holy water to kill a zombie.
They are scared of Zombie Repellent!
There's a bug in Remix where you can set a zombie on fire in water by putting it in the ocean, and dropping any electric object that will explode when wet, like a robot, or conduct electricity through water, like an eel. Since the explosion is electric, the zombie will burn. This is only possible if the zombie has enough health to resist the explosion, or it will die.