From Dragon Ball Encyclopedia, the ''Dragon Ball'' wiki
Grand Kaioshin (大界王神, Daikaiōshin; FUNimation "Daikaioh", Viz "Dai Kaioshin"; Literally meaning "Great World King God") is a Kaioshin.
Grand Kaioshin managed to save East Kaioshin from Ultra Boo's attack and unleashed a powerful attack of his own that literally blasted Ultra Boo to pieces, but was absorbed seconds later. After Grand Kaioshin was absorbed, Ultra Boo gained a new form that looked remarkably similar to Grand Kaioshin. This "Fat Boo" would continue to show Grand Kaioshin's spirit within him and later even become Mister Satan's friend. Grand Kaioshin's presence within Fat Boo pacified him. He was also very peace-loving and would gorge himself with food.
Grand Kaioshin appeared in Dragon Ball Z: Buu's Fury