Creeper

Creepers are hostile mobs that were added in Update 0.4.0. They spawn in light levels of 7 or below. They pose a significant threat to new players, due to their dangerous ability to explode.

Offense
Creepers follow the player when they are within 16 blocks, and attack by exploding. They make a hissing sound before doing so.

Combat
It is best to use a Bow when fighting creepers, however a strong sword like an Iron or Diamond sword can also be used. Another possible method is to ignite the creeper with Flint and Steel and run away, but this way can damage the terrain and cannot drop its loot. Wolves are not recommended while fighting with Creepers due to that their explosions can kill the Wolves very easy.

Charged Creepers
Charged Creepers (AKA Electrified Creeper) are sub-types of regular creepers that were added in Update 0.12.1. They only spawn when lightning strikes within a 5 block radius from a creeper, however, this is very rare. They have a much larger explosion, and do much more damage to the player and terrain. When they explode near a zombie, skeleton or creeper, the will cause the mob to drop his head.

Trivia

 * Creepers were created when Notch was programming the Pig. The model went wrong, and thus he created the creeper.
 * Creepers can be very hard to see in large grassy biomes, due to their green color.
 * Creeper Explosions cannot break blocks in Water.
 * It will still harm The Player and Mobs nearby.
 * Ocelots and Cats scare Creepers away.
 * When Creepers explode in a slab, it will destroy nothing but the slab.
 * Creepers do not make any noise when approaching players, thus often taking them by surprise, but do make a hissing sound when about to explode.