The Number One Hyperactive, Knucklehead Ninja Joins the Fight!

is episode 14 of the original Naruto anime.

Synopsis
Naruto finally joins the battle on the bridge. Sasuke is having a hard time fighting Haku and is trapped in Haku's Demonic Mirroring Ice Crystals. Kakashi is unable to help them, as he is dealing with Zabuza while protecting Sakura and Tazuna. He orders Sasuke to continue attacking the mirrors from within while Naruto attacks from outside. Unfortunately, Naruto is oblivious to Haku's jutsu and enters the cage of ice mirrors. Sasuke tells Naruto that he is a complete loser and that now they are both trapped. After a little arguing, both agree to work together. Haku reveals that he doesn't like to kill his enemies but will do so if he must.