1. The Tobi Identity Theory
During the Great Ninja War, Tobi was introduced as one of the main antagonists. Many fans speculated about his true identity since he concealed his face behind a mask. A widespread theory was that Tobi was none other than Uchiha Obito, a former comrade of Kakashi who was seemingly buried under a boulder. This theory gained a lot of attention and was eventually confirmed when the mask fell, revealing Obito as Tobi.
1. The "Naruto is a Reincarnation Avatar" Theory
This theory stems from Hagoromo Ōtsutsuki's revelation, the first shinobi to possess the power of the Rinnegan. He explained that he and his brother Hamura were reincarnation avatars of the Rikudō Sennin, the progenitor of shinobi. Some fans speculated that Naruto and Sasuke might be reincarnation avatars of Hagoromo and Hamura, which could explain their unparalleled powers and destinies. This theory was partially confirmed when it was revealed that Naruto and Sasuke are the reincarnations of Asura and Indra, the sons of Hagoromo.