Waggish is an adjective that means playful or mischievous.
Waggish comes to us from Old English. A Wagghalter is a now obsolete English word from centuries ago that referred to someone likely to be hanged — presumably from their playful for mischievous behavior. In more recent years we can refer to waggish behavior in less serious terms, for example: At first, I panicked when I saw what appeared to be a snake on my office chair. I soon realized this was just a waggish prank by a co-worker.