prankster
A person who often plays harmless tricks to be funny.
A prankster is someone who loves playing pranks: harmless tricks meant to surprise or confuse people in funny ways. A prankster might put salt in the sugar bowl, swap the contents of two identical boxes, or hide a toy spider where someone will find it unexpectedly. The key word is harmless. A true prankster wants to make people laugh, not cry.
Good pranksters understand timing and know their audience. They can tell the difference between a trick that will make everyone giggle and one that will hurt someone's feelings or cause real problems. Switching the labels on your dad's dresser drawers might be funny; hiding his car keys when he needs to get to work isn't.
Famous pranksters include the Weasley twins from the Harry Potter books and the trickster characters found in stories from cultures around the world. Some people have a reputation as pranksters because they're always thinking up clever schemes to amuse their friends and family.