Austin Mahone + The Vamps + Fifth Harmony + Shawn Mendes

Texas teen Austin Mahone attained celebrity the YouTube way in 2012, with his cover of Justin Bieber's "Mistletoe," beating the Beebs's original in terms of views. A few other key facts you should know about the popster: His fans call themselves Mahomies, and his biggest single to date, "Mmm Yeah," features the ubiquitous Pitbull.