Viva Dojo Challenge! Youth is All About Passion!

is episode 193 of the original Naruto anime.

Synopsis
Rock Lee is hungry for a sparring match, but has no one to spar with. He builds his own dōjō in the hopes of attracting challengers. Might Guy is so inspired by Lee's motivation that he puts on a disguise so that he can serve as the challenger that Lee seeks. But before he gets to challenge Lee, Guy is sidetracked by a mission. An intruder then shows up to spy on the village by impersonating Guy, but he unintentionally gets caught in Lee's overzealous training match. Naruto takes over for him, and fights evenly with Lee, and the intruder takes on Lee's form, but runs into the real Guy, who has come to take the challenge, and is easily defeated. Guy, hearing of the intruder's identity, drops him off in Tsunade's office, angering her.