Many believed that Sonic did not have fangs simply because they had never seen them when he smiled and quite often this led to the belief that he could not be menacing or scary due to his reserved demeanor, believing every soothing word spoken by his chatty mouth.

Shadow was an exception to this rule - the blue fool never revealed his secrets to the end, especially keeping to himself to have an advantage several steps ahead, that's why the black and red hedgehog never believed those "innocent" smiles, seeing in every one a hint of a smirk.