After Naruto defeated the kyuubi and took its chakra, Kurama confessed that Naruto look exactly like the SO6P in that state. The SO6P is seen as a figure with the a necklace of 6 rings which look like the tomoes of the sharingan. This was how Naruto looked when he took the kyuubi's chakra (Anime episode 247). I think the SO6P reserved some of its chakra........................