Mysterious Waylon is a limited-time premium costume for Smithers that was released on May 20, 2020, as part of the Pride 2020 Event. It was unlocked upon the completion of Draggle Rock.
The Mysterious Waylon is the drag queen alter-ego of Waylon Smithers. Marge met them at Draggle Rock, among other drag queens, and they all took part in a song and dance on stage.