Chicken Jockey

Chicken Jockeys are an extremely rare mob. They consist of a Baby Zombie, Baby Zombie Villager, or Baby Zombie Pigman riding a Chicken.

Behavior
Chicken Jockeys run around like Baby Zombies, instead of using the chicken AI.
 * Even though the Zombie AI is used, the chicken still randomly lays eggs.
 * Chicken Jockeys will not avoid bumping into walls that would potentially suffocate the Baby Zombie.
 * 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.
 * Like Zombies, the Chicken Jockey 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 take suffocation damage.
 * Chicken Jockeys can pick up/equip ground items.
 * Will ignore attacking the Player if the chicken notices him/her holding seeds, and will follow like a normal chicken.

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 10x6x10 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 command to spawn a Chicken Jockey is
 * This is not exactly the same mob, but it is close, the real Chicken Jockey is positioned lower on the Chicken's back, which you can get by spawning a large number of zombies, do this in daylight so adults burn. Then kill the babies that don't have a chicken to ride.
 * 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 they can spawn in the Nether, eggs, feathers, and raw chicken are now renewable in that dimension, without having to bring eggs from 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 Instant Health 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.
 * Chicken Jockeys and Spider Jockeys are the only mobs that 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.