Wombats are the only known animal that poops in cubes

A wombat's intestine has stiff and flexible sections that squeeze its waste into sharp-edged cubes, not the round pellets most mammals produce. The flat faces stop the droppings rolling away, so a wombat can stack them on logs and rocks to mark its territory. The finding won its researchers a 2019 Ig Nobel Prize in Physics.

— Patricia J. Yang et al., Intestines of Non-Uniform Stiffness Mold the Corners of Wombat Feces — Soft Matter, 2021