Originally Posted by Tmoore
good theory but does anyone else think that tobi can be a edo tensei summon gone wrong?
I don't think so, there isn't any evidence to point that way, except for the fact he claims to be the "immortal Madara" and Madara is supposed to be dead by now (or 100 years old). Edo summons regenerate very quickly when dmgd and Tobi doesn't.
On Tobi = Shisui theory, the thing that seems implausible to me is that Shisui would have the mangekyo sharingan when he attacked Konoha and then hide it for 5 years and live in Konoha before striking again. He would also have to be older than Itachi by at least 7 years (to look the way he did vs Minato). Finally when Tobi was alone trying to take Shisuis eye he talked about Shisui in third person, instead of saying "my eye" he said "Shisuis eye".