Diprosopus

Diprosopus (Greek διπρόσωπος, "two-faced", from δι-, di-, "two" and πρόσωπον, prósopon, "face", "person"; with Latin ending), also known as craniofacial duplication (cranio- from Greek κρανίον, "skull", the other parts Latin), is an extremely rare congenital disorder whereby parts (accessories) or all of the face is duplicated on the head.