Use the word knavish to describe someone who is mischievous, like a rascal or a hooligan. Their knavish behavior might seem playful, but it can be dangerously thoughtless.
Since the 14th century, this adjective has been used to mean "low or vulgar" or "like a knave" though both knave and knavish are rarely used these days. A knave was originally simply "a boy." As time went on, the word gained negative connotations, meaning "rogue or rascal" by the 1200s. So anyone who acts in a rascally way — playing pranks, being disobedient, or teasing little kids — is knavish.