Originally posted by: Aion
The 4th is not naturo, because the 3rd used the same jetsu on Orochimaru. Did he change into a baby third? no.
Well, the nine-tails and Orochimaru differ in power GREATLY. So the same jetsu used on Orochimaru would have way different effect. Another theory also discussed was that the 4th wanted to harness the amazing power of the ninetails and use it as an asset to Konoha. I don't think Sarutobi would want anything of Orochimaru even living in anyone. Possibly, ninetails is unabled to be consumed, but just sealed, like that guy said up there.
Naruto actually being the 4th is a little crazy, but its still a theory for discussion. Like many others think, Naruto is probably the son or relative of the 4th.