"Eat or be Eaten: Panic in the Forest" (喰うか喰われるか!エサになったナルト, Kū ka Kuwareru ka! Esa ni Natta Naruto) is episode 28 of the original Naruto anime.
Naruto has to pee and Sakura hits him and makes him go pee in a bush. When he comes out, Sasuke starts hitting him and explains to Sakura that this person is not Naruto because Naruto had a scar on his cheek. With his identity being compromised, the Ameninja ditches his disguise and fights Sasuke, who defeats him while spotting the real Naruto, freeing him after he beats the Ame-nin.
Sasuke tells the others that Team 7 needs a password, although the one he chooses is too long, with Naruto struggling to remember it before a powerful gust of wind separates him from his team. Just as he reorients himself, Naruto finds himself swallowed by a giant snake. When Sasuke and Sakura later meet up with who they thought was Naruto, Sasuke suspects something is wrong when "Naruto" repeats the password word for word. Sasuke explains that the real Naruto would not have recited such a difficult password, hence why he chose a lengthy one, and the impostor revealed to be the Kusagakure ninja Shiore. Swallowing his scroll, Shiore paralyses Sasuke and Sakura with visions of their deaths.
Sasuke succeeds in regaining his composure and getting himself and Sakura away from Shiore. Meanwhile, Naruto uses his Shadow Clone Technique to burst out of the snake. Once freed, Naruto quickly comes to his friends' aid as Shiore corners Sasuke and Sakura.