This animal always gives birth to identical quadruplets

Nine-banded armadillos reproduce through a quirk called polyembryony: a single fertilized egg splits into four separate embryos, which develop into four genetically identical siblings, always the same sex. It's the only mammal known to reliably do this every time it reproduces. Because the litters are natural clones, armadillos have been useful to leprosy researchers studying how the same genetic background responds to infection.

— Wikipedia contributors, Nine-banded armadillo — Polyembryony in Dasypus novemcinctus