In the Japanese versions, Naruto often ends his sentences with "dattebayo" or "(verb)-ttebayo", and as such Naruto has a unique style of speech. In the Japanese language, an ending can be added with no meaning to make the tone sound more tough, childish, girlish, or many other changes depending on the many existing endings. "-ttebayo", which is not a well-known ending, has no literal meaning and cannot be translated, but carries the connotations of the speaker being uncultured, brusque, and seeming tougher than they really are.In the English anime and video games, he often says "Believe it!" to fit with the mouth flaps of "-ttebayo".
Shikamaru got his information wrong, dattebayo.