A rapscallion is a mischievous jokester. Instead of getting angry when he realizes his shoelaces have been tied together, your grandfather might say, "Which of you rapscallions is responsible for this?"
Rapscallion is an old fashioned word for "scamp" or "scoundrel." It's most often used in a lighthearted way: "Some rapscallion seems to have replaced the cream in my Oreo with toothpaste — then again, it is April Fools Day!" Rapscallion, first used in the 1600s, was originally rascallion, a fancier version of rascal, which comes from the Old French rascaille, "rabble or mob."