"Chūnin Challenge: Rock Lee vs. Sasuke!" (気合い120％ ナウでロックな挑戦状!, Kiai Hyaku-Nijū Pāsento Naude Rokku na Chōsenjō!) is episode 22 of the original Naruto anime.
Sasuke has attracted the attention of Rock Lee, who challenges him to a fight. Lee is not only interested in seeing how his skills match up against a descendant of the Uchiha clan, but he also has a crush on Sakura, much to her dismay. Feeling neglected in his teammates' shadows, Naruto offers to fight in Sasuke's place. Without wasting time, he charges, but is easily knocked out by Lee. Lee explains that they cannot beat him because he is the strongest of the Konohagakure genin right now. Now interested, Sasuke accepts his challenge. Sasuke attacks and is met by Lee's Leaf Whirlwind and gets knocked backwards. As he gets back up, he prepares to use his Sharingan to figure out Lee's technique. He again charges Lee, but again, Lee is able to hit him. Lee explains that his moves are neither ninjutsu or genjutsu, but mere taijutsu, also known as martial arts. With hand-to-hand fighting, Sasuke's Sharingan isn't helpful because even if he can see the techniques, his body cannot move fast enough to react. Lee uses the Shadow of the Dancing Leaf to kick off his next attack in order to finish off Sasuke, but a large turtle stops his attack before it hits.
The turtle seemingly reprimands Lee for using his forbidden technique, leaving Naruto to think the turtle is Lee's sensei. Might Guy (Lee's actual sensei) appears on top of the turtle and punches Lee hard in the face as punishment. Guy proceeds to hug Lee, and the two cry. Team 7 are dumbstruck, and Sasuke can't believe he was beaten by what he perceives as a freak. Guy asks the team how his eternal rival, Kakashi, is doing. He's ahead in the match record, which stands at 50 wins and 49 losses. Guy also says that he is much faster and stronger than Kakashi.
When Guy leaves, Lee confesses that he is not the strongest genin - Neji Hyūga, Lee's teammate is. Naruto needles Sasuke, saying that Lee obviously trains harder than Sasuke. In the end, the team focuses their attention on the Chūnin Exams.