Continuity mistake: Throughout the entire show, the stone faces of the Hokages change, whether it is up, down, facing to the left, facing to the right, facing forwards, etc.
Continuity mistake: In "Enter: Naruto Uzumaki!" While Iruka is thinking about what the Hokage said about Naruto, he's in bed without his green vest. When Mizuki pounds on the door, Iruka sits up and he's wearing the vest. But, when he opens his front door, he's not wearing it again.
Continuity mistake: In "Sasuke and Sakura: Friends or Foes?" Throughout the episode Sakura has a circular mark at front bottom part of her dress, except when she was racing with Ino to get to class.
Continuity mistake: In "Enter: Naruto Uzumaki!" When Mizuki and Iruka were talking in the forest Iruka's vest had a cut on the shoulder, but when Iruka said "How's that?" the cut was gone.
Continuity mistake: In "Enter: Naruto Uzumaki!" Iruka set a log down next to him (The one disguised as the Book of Seals), but when Mizuki was about to throw the giant shuriken, it's not there anymore. It reappears in every other shot though.
Continuity mistake: In "Enter: Naruto Uzumaki!" During the confrontation scene with Naruto, Iruka and Mizuki, watch the shoulder of Iruka's vest. First, it's pinned to the wall behind him after Mizuki first attacks. When Iruka first yells at Mizuki not to tell Naruto the truth about his past, his vest is free from being pinned, yet when he yells at Mizuki the third time to stop, his vest is again pinned to the wall and Iruka rips the shoulder of his vest out from the kunai that pinned it there.
Continuity mistake: In "Enter: Naruto Uzumaki!" When Sasuke goes up to perfrom his transformation jutsu, there is only one student next to Naruto. In the next shot Naruto is in between two students.
Continuity mistake: In "Enter: Naruto Uzumaki!" When Naruto does the Kagebunshin no Jutsu (Shadow Clone Jutsu) and all the clones are shown, the scroll that Naruto stole is missing. But, it reappears once more after Naruto has beaten up Mizuki.
Other mistake: Often, when Sakura is about to punch Naruto, he has enough time to dodge her attack but never does it.
Answer: That is just a style used by some animators. It is easier to keep the arms in one position than to draw them in motion. And it makes it look funnier.
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