No one ever said it was easy being a pop star. Sure, there's the obvious glitz, glamour, and gratis clothes, food, and shampoo (i.e. EVERYTHING'S FREE WHEN YOU HAVE MONEY), but too often do we forget the ugly side of a pop star's life: getting followed around by noxious paparazzi cameras, unrealistic expectations of perfection, nitpicking press criticism, people like us charting your rise and fall, not even being able to so much as enjoy a 15-minute doughnut break without being overrun by hoards of screaming fans, and sometimes getting busted for a little weed on your tour bus. (And to that we say, after all Justin Bieber has done for us, LET THE GUY HAVE A LITTLE DIME BAG, OK? JEEZE.) All that's gotta wear on a person, right? Especially when they've been famous for most of their adult life? And how do we know when things are REALLY bad? Like, when does harmless birthday clubbing, fashion gas masks, and shirt removal turn into a full-fledged, head-shaving meltdown? Well, prepare to find out in MTV's "The Meltdown Index," starring Britney Spears and Justin Bieber, two impossibly world-famous pop stars, each with their own strain of "whoopsie" moments and career gaffes. Click on the image to enlarge!

Now presenting: the Justin Bieber/Britney Spears Meltdown Index.