"A New Chapter Begins: The Chūnin Exam!" (新章突入!中忍試験だってばよ, Shinshō Totsunyū! Chūnin Shiken Dattebayo) is episode 20 of the original Naruto anime.
After completing their mission in the Land of Waves, Team 7 returns to Konohagakure. Although Sasuke saved Naruto's life their teamwork seems to have got even worse than before with Naruto intent on beating Sasuke causing him to mess up on subsequent missions. Kakashi decides that their teamwork is too off that day and sends them all home. Before leaving Sasuke tells Naruto in a matter-of-fact manner to simply get stronger than him before telling Sakura who had suggested that the two work of their own teamwork skills, that she was worse than Naruto. Konohamaru and his two friends: Udon and Moegi would later stalk Naruto. As antics ensue, Konohamaru accidentally bumps into a foreign ninja who he then insults causing the latter to threaten to kill him. Naruto attempts to attack the newcomer but is tripped by his invisible attack. Just as the mysterious ninja is about to hit Konohamaru, Sasuke saves the day by forcing the ninja to drop Konohamaru. Just as the mysterious ninja is about to attack Sasuke, another one, appears telling the latter to stop playing around. Meanwhile, all the jōnin are gathered along with the Third Hokage. He announces that the chūnin exams will take place in seven days on July 1.
Interestingly, the key Naruto uses to lock his door is fashioned like Pakkun, one of Kakashi's ninken.