This weekend on The iHeartRadio Countdown with Mario Lopez professional dancer turned 'Dancing With The Stars' judge Derek Hough Zooms into the show! The new season of DWTS kicks off on Monday night on ABC with a new cast of celebrities and Derek will judging the competition. Plus he's going to be kicking off a new Las Vegas residency this fall as well! So we'll catch up with him, countdown the top 20 songs in the country, play some throwback classics and more! Tune in!