An Unrivaled Match: Hokage Battle Royale!

is episode 71 of the original Naruto anime.

Synopsis
The Hokage battle begins, and all three Hokages exchange varying elemental attacks. To help him in the uneven fight, the Third Hokage summons Enma and has him transform into a staff. In response, Orochimaru brings out his Kusanagi sword. The Third is repelled by the First and Second, and he discovers that they cannot be damaged in their present state. Orochimaru then shows the Third the fruits of his quest to gain immortality. Peeling away his face, Orochimaru reveals the face of a girl whose body he has taken; Orochimaru's key to living forever is to take the bodies of others to extend his lifespan.