Despite his massive success, Andy Cohen still has things to check off in his career. The Bravo boss recently marked the 15th anniversary of his hit talk show Watch What Happens Live, but he’s not slowing down on spilling the tea with A-listers anytime soon. Cohen chats exclusively with OK! about who he still wants to have as a guest on the hit chat series, balancing his busy life with fatherhood and his partnership with Fresca Mix for their Fance Ice sweepstakes. “There’s a lot of music people that haven’t done WWHL that I would love [to get on the show]. I’m a big music fan,” he explains of w…