Celebrities took to Twitter to remember disco queen Donna Summer, who died of cancer at the age of 63 Thursday. Janet Jackson tweeted: "We will miss Donna Summer! She changed the world of music with her beautiful voice and incredible talent." Dolly Parton: "I can't believe we've lost another wonderful singer. Donna, like Whitney, had one of the greatest voices ever …" Mary J. Blige said Summer was "truly a game changer!!!" And Swedish pop princess Robyn tweeted: "I FEEL LOVE FOR YOU."