Crazy creeks were a big fad years ago during my time at summer camp. They are lightweight, portable chairs made of foam that sit on the ground. Your body weight is used to make the chair sit upright comfortably. The chair can be adjusted using adjustable straps.
Crazy creeks are desirable because they are lightweight and a comfortable way to sit outside on the ground. You can bring them with you on a hiking trip or to a picnic.