Creeper's are civilized yet destructive creatures. They also like blowing up your stuff ALLOT. They especially like killing your livestock and destroying your crops. The design is more complex than what meets the eye. Their unique design all comes from the square, green like structure but the most fascinating part is the hidden explosives hidden under their thick green skin. First you hear a hissing sound like TTTSSSSSSSS and then comes the BOOM!!! It's like you never saw it coming and even if you survived you got a gaping hole in the ground or it blew up your frickin house. The unique design of it is the reason minecraft is so popular. That is why notch is a good designer in monster like green thingies with TNT inside there skeletons and for some reason they kill themselves to kill you or blow up your stuff.