Tobi can't be Shisui. He was found dead in a river and based on his profile he was a stand up guy. He may not even have been a Uchiha. I think he may be some sort of experiment by Orochimaru from the early days, while he was trying to splice senju and uchiha cells. At first sight, he seems to know quite a bit about Madara, more than an average person would know. But, should not one of the greatest clan member's biographies be well known throughout the Uchiha Clan? And, stated from memory, EdoMadara didn't say anything about Tobi to Kabuto-Controlled EdoMuu. In the few instances that Tobi fights, he seems to lose appendages with regularity, and what is shown of his body seems to be similar to the make-up of Zetsu. Thoughts?