Creeper

The Creeper is a hostile mob that will blow up on contact. It will make a distinctive hissing sound, not to be confused with a spider or cave spider, then blows up. They are also the mascot of Minecraft and Mojang Ltd..

Appearance
Creepers are green plantlike creatures with black pixelated holes in their face. They walk up to you hissing then blow up if you don't move away. If shocked by lightning, they become a charged creeper, or lightning creeper.

How they became the mascot and other appearances.
It is unknown why the creeper became the mascot. Someone might have thought they were the rulers of the world or were part of nature. But, it is still unknown. A creeper can be seen on the "A" in the Minecraft logo, and can also be seen on multiple minecraft shirts.