[Strike Witch]

'Dattebayo' is a Japanese vocal quirk. Japanese people have several accents, one of the most famous being the Kansai accent which is often translated to a Southern accent when localized. The difference between our concept of accents is that Japanese accents often mean changed ending words or sentence finishers. It also complicates things when individuals often change their own sentences depending on how they want to sound.

For example, a manly person might use "-ze", a person from Chubu might us "-Yaea", etc. Of course because the way you speak can show what kind of character you are, Japanese writers and manga-artists and film directors use vocal quirks to help audiences understand a character more. So for example, a rich snob might end their sentences with "desu-wa", a foreigner might use "desu" way too much or not at all, And stupid monster characters often had some nonsense word or word vaguely-related-to-what-they-look-like tacked on the end, to make them sound silly to Japanese children.

Dattebayo is one of these, it's basically "You know?" and is there to show what a childish and stupid guy Naruto is.