Céline Dion caused a fan frenzy in Paris returning from her top-secret Olympics rehearsals! The stage is set for her ultimate comeback at Friday’s opening ceremonies, after she retreated from the spotlight amid her battle with stiff-person syndrome. Lady Gaga was also swarmed by fans as she headed to dinner in Paris before her rumored appearance. According to Variety’s executive editor of international Elsa Keslassy, Gaga has been seen rehearsing on the Seine on the floating piano.