Fans are pissed at Katy Perry! The Firework singer has sparked backlash across social media after derailing a birthday surprise. There's currently a video that has people up in arms from a backstage moment at one of Katy's Lifetimes Tour shows. In it, her crew gathers to surprise her with a cake for her 41st birthday! Super cute, right? The Thinking of You singer is clad in her tour wardrobe and blows out the candles as her crew sings and cheers in celebration of her. But what comes next is what's riling up fans...