Board Thread:The Panopticon/@comment-26975268-20130407222910/@comment-26975268-20130408114347

Very true. In fact, we've already encountered a sentient sun and a sentient planet!

However, the Doctor calls it a planet only before he meets the God. Afterward, he specifically avoids the inevitable word. The best description we're given of the Old God is "parasite god." No indication that he's actually a planet.