I'm usually kinda bored by silly pranks artists pull on each other in concert . . . but this one made me grin. 

During a recent stop on the CMT Tour, LOVE AND THEFT and FLORIDA GEORGIA LINE surprised JAKE OWEN by hitting the stage in their underwear . . . or "adult diapers" . . . with pacifiers in their mouths and "bottles" of beer.

They were goofing on Jake becoming a father last month. And they stuck with the plan by hanging around and helping Jake perform VAN HALEN'S "Jump".

Here's the video: Love and Theft's STEPHEN BARKER LILES enters first, and his bandmate ERIC GUNDERSON follows him. The two Florida Georgia Line dudes are TYLER HUBBARD with the longer hair . . . and BRIAN KELLEY.