Watch on SFlix. Hosted by actor/comedian John Leguizamo, Nickelodeon's Mega Music Fest will feature celebrities like Colbie Caillat, Wyclef Jean, and The Roots performing never-before-seen duets with Dora the Explorer, the cast of 'Yo Gabba Gabba!', and Kai-Lan, plus special appearances by The Laurie Berkner Band, The Fresh Beat Band, and even a few surprise cameos. John Leguizamo will need YOUR preschooler's help to make sure the show goes on!