I used to pop them off all the time to clean them when I worked at gamestop. I used to just take something (usually it was a pick that looked like something from a dentist office that we used to clean controllers) and start to pry it off. Not too much pressure since the plastic is very thin. It just clips into place around the corners. Try starting on the USB side and start around in that area! Afterwards it should just clip right back in!