Superstars often seem to incubate behind closed doors, honing their craft until they can burst on the scene and stun us all into buying whatever they make. In reality, few masters of the celebrity biz can make it without testing their wings in the kinds of small, often embarrassing public venues they wouldn’t be caught dead in after the Grammys are in hand. Whether it’s the hip-hop mogul who once washed the cars of record label execs or the many who sang total nonsense on TV, there isn’t one one among our list of superstars who didn’t lick a boot or two to get to the Promise Land.