So Chuck Shirley (some of you know him as God) created the universe, right? Let's put aside the multiverse stuff for the moment and focus on the fact that he made the universe. So he made the milky way, the solar system, and all the planets in it, right?
So what if after he'd made all nine planets, he just looked back at them and instead of going, 'Whew, Job done, Planets created, I can par-tay now', he went 'Most of these planets look fine, and Earth in particular turned up great. Plants are already growing there, and I've got a good feeling about it. So I'll just let these properly-functioning-celestial-bodies be, and pay more attention to the others. Venus, the moody little planet she is, is having storms and her temperatures are fluctuating immensely; it's like she's sworn not to let life exist there. Saturn is being vain as always and wanting everything to himself, I've gotta talk to him about consuming every pretty thing around him and keeping it for himself. And Pluto has this complex about not being good enough, and I gotta talk him out of the low self-esteem and assure him that he IS a planet, no matter how much the others say otherwise.'