Creeper

The creeper

The creeper is the iconic unofficial mascot of the hit video game Minecraft. A hostile mob, it spawns in the overworld in poorly lit areas with a light level of 7 or less.

Behavior
The creeper will pursue any player in a 16 block radius, and if the player gets too close to a creeper (within a 3x3 block radius), the creeper will start hissing, flashing and expanding, and will explode after 1.5 seconds unless the player leaves its blast radius before it does so. Its explosion will harm any mobs that are within the blast radius (7 blocks).
However, the creeper is terrified of cats and ocelots, and will run away from them at all costs, even if there is a player nearby to blow up.
Interestingly, if a creeper is inflicted by a status effect, it will affect any mobs with that status effect if they happen to be within its blast radius when it explodes.

Info
Blast Radius: 7 blocks
Health points: 20 (10 hearts)
Experience dropped (when killed): 5
Size: 1.7 blocks (height) by 0.6 blocks (width)