VIDEO : Justin Bieber Enlists Rock Legend Steven Tyler to Help Promote His Upcoming Single

Justin Bieber 's star-filled countdown just keeps growing! Steven Tyler, Kevin Hart, and Ellen Degeneres are the latest celebrities to help Justin tease his upcoming single, "What Do You Mean?" With his single dropping on Friday, Justin has pulled out the big guns and enlisted none other than rock legend, Steven Tyler, to promote his upcoming single. All month, Justin has been recruiting several other famous faces ? including new collaborator Mariah Carey and Kylie Jenner ? to promote the song. The 21-year-old Canadian first spoke of the headline-grabbing single when he stopped by On Air With Ryan Seacrest and announced its release date as Aug. 28th.