Past Speculation
Before Tobi is revealed to be Madara Uchiha, several fans hypothesized that he could be Obito Uchiha, as his only shown eye was the opposite of the eye that was inserted in Kakashi, which replace Kakashi's destroyed left eye in the manga-exclusive Kakashi Gaiden, and their similar hair styles. Also, they both act in the same goofy way, and Tobi has claimed to be a good boy, while Obito was a good boy. Furthermore, Tobi is seen to have pins in his body under the coat, and Obito's body was crushed. The spelling of Obito was also similar to Tobi, creating the fan reference of ObiTobi, or Tobito.
Another fan speculation is that Pain, who now is discovered to have multiple bodies, could have used the remains of Obito to reconstruct the body and revive Madara in the body of Obito, which contained Sharingan only within the right eye, the same eye that Madara has been shown using the Sharingan. It is also possible that Pain employed Kakuzu, who was able to reattach Deidara's arms after they were severed, and could have done similarly with Obito and Madara.
One more speculation is that Orochimaru, who was able to use the Summoning: Impure World Resurrection, as demonstrated in the fight with the Third Hokage, and who was once a member of Akatsuki, probably used or learned it there. And so, it is possible that the body of Obito has been reanimated and the spirit of Madara has been implanted into him using another forbidden jutsu.
Fans also speculated that Madara could also be Danzo. Tobi has bolts on the same arm that Danzo has covered up and they share similar hair styles. Not only that, he and Madara share the same hatred for the First, Second, and Third Hokage's teachings and philosophies. Madara also hates the Senju clan, and the First and Second were both Senju, and Danzo despises Tsunade for being the grand-daughter of the First. Danzo has the same eye covered up that Madara has his Sharingan. Kisame's revelation of Madara being Mizukage offers more support to this theory as Danzo's Root is said to use extremely similar methods to Kirigakure earlier on, the education that led to the village being referred to as the Village in the Bloody Mist. Also when Madara tries to reveal his Sharingan to Sasuke by taking off his mask we see that part of his face is heavily wrinkled, adding more to the possibility that he could actually be Danzo.
tako da- tnx za odgovor kakvom sam se i nadao. pitao sam se u stvari da li naruto ima rewatchability value... 
. Sam itachi je rekao da je on ustvari madara zasto bi on lagao.