Slime

Slimes are naturally spawning mobs that were added in Update 0.9.0. They are relatively rare creatures that generally spawn in caves, or random Underground chunks. Slimes spawn more during a full moon. Slimes will break into smaller slimes when attacked. They first appeared in the Beta build for Update 0.9.0.

Combat
Slimes jump at the player to attack, doing damage equal to their size. Upon dying, they will split into multiple slimes of smaller size, unless already at the smallest possible size, which is smaller than a block. However, the smallest slimes cannot damage the player.

Trivia
Slime
 * They don't drop slimeballs yet
 * In the PC version of Minecraft, slimes drop Slimeballs, but it is unknown what they will drop in PE, but it will likely be the same.
 * The smallest size of slimes will not do any damage to the player.
 * Killing the bigger slimes are recommended before taking out the smaller ones, as they will cause more damage to you, whereas the smaller slimes will do little to no damage.
 * Due to their ability to split into small slimes when damaged, all slimes except the smallest sizes do not die to fall damage, no matter how high they fall; therefore they are the only mob that can survive from the highest drops.
 * In the 0.10.0 they appear more frequently and easily.
 * Although they have no arms or legs, slimes can still swim.
 * Small slimes have the least amount of health out of any mob in Minecraft, with 1 heart.