Yubaba is the scheming proprietress of the Bath House. She is a witch whose powers include stealing people's names so they can't remember what they're called, thus are forever doomed to work in her bathhouse. She also can spit fire, so don't annoy her.
Yubaba has a twin sister called Zeniba who is her polar opposite but they both have huge heads, and she is the mother to a very fat baby. Quite frankly she's a terrible parent and coddles the boy too much.