Regarding that 'one eye'...

[HimuraKenshin]

I just had a crazy thought, what if the reason Madara only had one eye was because Izuna had the other one? Isn't it strange that he only took one sharingan eye, I mean, how many single-eyed uchihas are there? Why wouldn't he take both eyes if he had the opportunity?

Madara had his sharingan-eye on the left side while Tobi has (and always had) it on the right side, hence he can't be the long haired Tobi. Izuna on the other hand, under the assumption that Madara gave the other eye to him, would (or should? dunno how the eye transplantation-technique actually works) have his eye on the same side as Obito, therefore it's possible that he's the long haired tobi! Well, what do you think?

P.S.
I humbly apologize if anyone has mentioned this before. Personally I don't actually believe that the long haired Tobi=Izuna, I think that would just be too complicated. However there is a possibility (a reaaally small one though) that Izuna is if he was still alive at the time.

[Okami the butcher]

well he said it was a replacement sharingan which reinforces that idea the he gave his rinnegan to Nagato

[Kirikoe]

at this point anything is possible ... so i wouldnt believe if this was actually true i mean we have an old madara absorbing chakra from a tree with zetsu growing on it so.....

[HimuraKenshin]

well he said it was a replacement sharingan which reinforces that idea the he gave his rinnegan to Nagato

Yeah I know but what i'm talking about is the replacement sharingan, why does he only have one eye? I for one find it strange that he didn't take both, especially after learning that two eyes are better than one

[-Jiraiya-]

He said he left his "eyes" - plural with someone meaning he had loaned his 2 eyes to some one..

[HimuraKenshin]

He said he left his "eyes" - plural with someone meaning he had loaned his 2 eyes to some one..

Again, what I'm referring to is that replacement sharingan, not the rinnegan eyes he gave to nagato. So according to my logic this should've happend after he gave away his eyes to nagato.

If i remember correctly, izuna was missing his eyes so he would have just a single eye (like tobi) if he were given one

[edo tensai wilmaso]

im pretty sure he gave them to nagato , izuna is not in this story anymore.