Whether it's a desire to feel liberated or an attempt to boost a sagging career, for decades stars including Marilyn Monroe and Kim Kardashian West have found reasons to bare it all on the glossy pages of Playboy. Some may think that throwing modesty out the window is the only criteria that's needed to become a Playmate, but that's not the case. Hugh Hefner, who turns 89 on April 9, 2015, has set the bar high ... and to prove it, we're taking a look back at the most famous Playboy rejects, starting with Bridget Marquardt. A few failed test shoots didn't stop this bombshell from eventually stripping down for the men's mag. Despite her early rejections, Hef invited Bridget to move into the Playboy Mansion and become one of his three girlfriends -- along with Holly Madison and Kendra Wilkinson -- then asked the bevy of beauties to pose for Playboy multiple times. Click through to see more!