Use the word raffishly to describe anything that's done in a careless, mischievous way that still manages to be charming. When the class clown grins raffishly after playing a practical joke, you can't help but laugh.
Someone who acts raffishly is a bit of a charming scoundrel. You might describe your friend as dressing raffishly, in jeans with torn knees and attractively tousled hair. Your favorite singer acts raffishly when she laughs off a reporter's questions and swaggers away. This adverb comes from raff, once used to mean "people" or "people of a lower sort."