Zombified Piglin

Zombie Pigmen are neutral mobs that first appeared in Minecraft alpha. Now in Beta 1.5, pigs that are struck by lightning will become a zombie pigman (this was confirmed by Notch). Cooked porkchops are dropped by dead Zombie Pigmen, and are therefore a renewable source of food in the Nether.

Behavior
Zombie Pigmen wander around aimlessly, avoiding cliffs and Ghasts. If you stand near a Zombie Pigman, it will turn its head towards you for a few seconds, then resume its wandering. Zombie Pigmen spawn in packs of 4-10 and tend to stay together. It seems, however, if space is limited (for example, a narrow tunnel), they may spawn in smaller groups or even alone. Attacking one Zombie Pigman will cause the entire group to become hostile, often swarming the player. This can make them very deadly when in a group due to each zombie pigman dealing 3 full hearts of damage. If the player moves a certain distance from a pack, waits a while or leaves the Nether and returns, they will become neutral again. Switching the difficulty to Peaceful will cause them to de-spawn completely and reset their neutrality in other difficulties.

Zombie Pigmen can appear on very rare occasions in the regular world in Beta 1.5 because of lightning. If a pig is struck by lightning it will turn into a Zombie Pigman.

Trivia

 * Zombie Pigmen are mostly immune to lava and fire. However, they can take damage from lava as it does not prevent falling damage like water does. Therefore, if they float in place long enough, they can accumulate enough falling damage that simply die the moment they touch any surface, including land and the bottom of the lake or stream.
 * Despite wielding a golden sword, they deal 3 (Normal Mode) damage instead of the normal 2 damage.
 * Zombie Pigmen, prior to the 10th of November 2010 update, would never forgive the player for attacking them. Now after a certain amount of time has passed since an attack, they will become neutral.
 * Zombie Pigmen can travel to the Overworld using Portals.
 * The skin file has "thx xaphobia" written on it, as a credit by Notch to the skin's original creator.
 * When spawned in the real world due to a pig being struck by lightning, fire will appear on Zombie Pigmen at random times but quickly disappear.
 * Zombie Pigmen, as well as Ghasts, are capable of drowning if under water or lava for too long.
 * The green liquid in the Zombie Pigman skin was originally blood red, but got changed due to users expressing a liking for the existing lack of blood anywhere in Minecraft.
 * Oddly enough, when the crosshairs are set on a zombie pigman, the inventory will turn transparent.
 * A direct hit by a Ghast's fireball will cause a Zombie Pigman to run directly towards the Ghast and attempt to attack it. This behavior has only been observed if the Ghast is touching the ground, usually occurring when the Ghast spawns under a low ceiling. This is likely because Zombie Pigmen cannot find a path to an airborne Ghast. Only the Zombie Pigman which was hit by the fireball will attack the Ghast - nearby Zombie Pigmen will not change their behavior.
 * As of Beta 1.5, Pigs struck by lightning will be transformed into Zombie Pigmen.
 * Despite wielding a golden sword, they do not drop them when killed, and they also never break.
 * Zombie Pigmen were the first predominantly neutral mob in Minecraft.
 * Zombie Pigmen will not catch on fire when hit by lightning.

Drops

 * 0-3 Cooked Porkchops

Bugs

 * If a Zombie Pigman falls from a height of about 3 blocks and hits you it kills you.