God is an omnipotent being first appearing in the Season Three episode, "Are You There God? It's Me, Jesus". He is the father of Jesus.
Jesus sought him out in order to make an appearance during the new years eve millennium party. Everyone in town was expecting Jesus to do something special for the occasion, however God refused to make an appearance on Earth. This left Jesus to decide to do something else for the millennium, as he desired to be liked by the populace once more. When God does arrive he grants the townsfolk one answer to any question.