Should all be ashamed.

Its the dagger holder, strapped to their leg.

In fact, in one episode, during the chuunin exam #2, where sauske, naruto, and sakura are in the forst, when sauske attacks naruto or the other way around, not sure, the reason they say is because the transformation was done incorrectly, in naruto's case it was because of the gash on his cheek (which could of healed fast from kyurbis (spelling?) power.. but anyway) and the other instance it occured was because the shuriken holder was on the wrong leg.

The other's have already been explained.