It turns out that Naruto stopped using the “Believe it!” catchphrase around the time of the Chunin exams, at least in the English dubbed anime. It was around long enough to be ingrained into every “Naruto” fan’s brain, though.
Naruto’s catchphrase was fairly polarizing among fans of the series, with some thoroughly enjoying it and others hating it. On Reddit, one user asked why the English dub removed the catchphrase after the Chunin exams if it was a popular phrase among the fanbase. The user liked the saying, which seemed to be the minority opinion. Other users commented on how they either found it annoying or just got used to how often Naruto said it. Redditor u/Alliedoll42_42 said, “Yuck no! Everyone made fun of it because of how often he said it.”
“Believe it!” wasn’t Naruto’s original catchphrase. In the Japanese dub and the manga, Naruto says “dattebayo” instead, but the phrase does not have a direct translation to English. Thanks to the show’s DVD commentary, we know the creators of the English dub decided to change the catchphrase to “Believe it!” since it matched the mouthing from the Japanese anime. Unfortunately, fans found the new saying so annoying they ended up scrapping it altogether.
A problem arose hundreds of episodes later when Naruto needed a way to recognize his mother, Kushina. In the manga, he discovers she’s his mother through their similar speech pattern because they share the catchphrase, but he no longer has a slogan in the dub. The dub creators revealed via the DVD commentary that they eventually settled on “ya know,” a slightly more accurate translation of “dattebayo.”