What is the shape of Saturn's moon Hyperion often compared to?

Saturn’s moon Hyperion is often compared to a sponge.

The comparison comes from Hyperion’s deeply cratered, porous surface. Its impact craters have sharp, steep walls and dark material filling their bottoms, making photographs resemble a giant natural sponge. Hyperion is not smoothly rounded like Titan or Rhea; its irregular shape is one reason it was the first known non-rounded moon discovered.

Hyperion’s low mean density, about 0.56 grams per cubic centimeter, suggests that it contains a great deal of empty space. Its porosity is estimated at roughly 42 percent. Because the moon has weak gravity and a loosely packed structure, impacts tend to compress the surface rather than excavate it normally, while some blasted material can escape permanently.

William and George Bond independently discovered Hyperion in the United States in 1848, and William Lassell found it independently in Britain soon afterward. The moon also rotates chaotically rather than keeping a predictable orientation. Its largest named crater, Helios, is about 140 kilometers across, while a much larger unnamed crater dominates part of the surface. The sponge analogy refers to texture and structure, not just outline.