King River Butterfly Is a supporting character in the Disney XD animated series, Star vs. the Forces of Evil. He is the king of Mewni, Queen Moon's husband and the father of Star Butterfly.
Despite seeming just as formal and strict as his wife, it is revealed in "Diaz Family Vacation" that he enjoys fighting monsters like Star does, whenever his duties as king bore him.
King and Queen Butterfly on Star's Mirror
"I didn't see you and you didn't see me."