The middle one hangs out with the other two so she can be the thinnest member of the group. The left one hangs out with jupiter for the same reason, and the middle one because it has an unusually fugly face. Left one probably deludes itself into thinking it's the "prettiest" member of the group. And jupiter hangs out with the other two because, well what else is it going to fucking do. The thing is practically too fat to breath. They probably bring it food or something.