Chicken Jockey

A Chicken Jockey is an extremely rare appearance of a baby zombie, baby zombie villager, or a baby zombie pigman riding a hostile chicken. They are easily killed with a durable sword but cannot be killed by leading it off a cliff. It will just slowly fly down to the ground without receiving any harm.

Behavior

 * Chicken Jockeys run around, instead of using the chicken AI.
 * The chicken does not lay eggs
 * Chicken Jockeys do not take fall damage, as the chicken flaps its wings quickly, slowing the falling speed.
 * The chicken moves at the speed of the baby zombie, which is much faster than a normal chicken.
 * Chicken Jockeys can track the player over a very large distance as they run very fast.
 * Like zombies, Chicken Jockeys will also track villagers.
 * Although a Chicken Jockey's hitbox is 3 blocks tall, the chicken can still run through 1 block high gaps. If the above block is solid, the Baby Zombie will suffocate.
 * Chicken Jockeys can pick up/equip items.
 * Chicken Jockeys ignore attacking players if the chicken notices him/her holding seeds, and will follow like a normal chicken.
 * Chicken Jockeys will not hurt a player in water.
 * Chicken Jockeys in flowing water will be separated into their individual mobs.

Spawn
Each baby zombie or baby zombie pigman that spawns has a 5% chance to spawn riding a chicken. This includes baby villagers turning into baby zombie villagers. There is an additional 5% chance of it mounting any existing chicken within a 10×6×10 box centered on the baby zombie's spawn location. In a chicken-free environment, this gives each spawned zombie a 0.25% chance of becoming a Chicken Jockey; if chickens are present, the chance increases to 0.4875%.

Chicken Jockeys may spawn with items equipped. Baby zombie pigmen versions of the Chicken Jockey will always have their Golden Sword equipped. Provoking the Zombie Pigman chicken jockey will cause it to attack, like a normal Zombie Pigman.

Trivia

 * The baby zombie's hitbox is larger than the chicken's.
 * Attacking the chicken may harm the zombie instead, unless the player carefully attacks its feet.
 * If the chicken moves too close to a wall two blocks high, the zombie half will take suffocation damage unless the upper block is transparent.
 * Since pigman chicken jockeys spawn in the Nether, chickens can now as a result spawn in that dimension. This means that feathers and raw chicken can be obtained without going to the Overworld.
 * When a Splash Potion of Harming is tossed at a Chicken Jockey, the chicken dies, but the baby zombie gains some health. Vice versa, if a Splash Potion of Healing is thrown at a Chicken Jockey, the chicken is healed, but the baby zombie takes damage (and may be killed). This makes healing them as a single mob very unlikely. A Splash Potion of Regeneration heals the chicken, but has no effect on the baby zombie.
 * Chicken Jockeys, like Spider Jockeys, cannot pass through portals.
 * It is possible to have a pigman chicken jockey in the Overworld by having a portal with a chicken near it.
 * It is also possible to have a generic chicken jockey in the Nether by killing a zombie pigman, spawning in normal zombies.
 * If the zombie happens to be a villager zombie, curing it will separate the formed villager from the chicken.
 * Unlike ordinary chickens, the chicken from a Chicken Jockey can despawn.
 * Chickens spawned as part of a Chicken Jockey do not lay eggs.
 * Using Name Tags to prevent despawning can be used to gather Chickens for Chicken farming, if Chickens do not naturally spawn in an area.
 * Chickens bred from two Chickens spawned as parts of Chicken Jockeys do lay eggs, however. They also do not despawn.
 * Chicken Jockeys can spawn from Zombie Spawners.
 * Chicken Jockeys are the second-rarest mob variant in Minecraft, with a 1:400 chance of a Zombie spawning as a Chicken Jockey. The rarest is the Killer Rabbit.
 * The baby zombie riding the chicken cannot catch fire from daylight, nor can it catch fire when it's not on the chicken because of the baby zombies AI.
 * The Wither will attempt to attack the chicken being ridden by the zombie, however the zombie will also take damage even though it is an undead mob.
 * Adult zombie and zombie pigmen can also control the chicken while riding on it, though they do not naturally spawn on chickens.