Naruto's Ninja Handbook

is episode 78 of the original Naruto anime.

Synopsis
Naruto's determination to save his friends helped him overcome the fear that Gaara had instilled in him earlier. Rejuvenated, Naruto summoned 999 shadow clones and performed a large-scale combo attack. To fend off the attack, Gaara completed his Shukaku transformation; he became the tailed beast in its giant form, destroying all of the shadow clones in the process. Using his sand, Gaara tried to crush Naruto, but Naruto summoned Gamabunta to break out of the sand at the last second. Gamabunta and Gaara exchanged blows, but Gaara forced himself to fall sleep, thus allowing the spirit of Shukaku to take over his body. Gamabunta was forced onto the defensive. Needing to get close to Shukaku in order to force Gaara awake, Naruto and Gamabunta performed a combo transformation to turn themselves into a giant nine-tailed fox to fight.