At the end of her July 22 Mayhem Ball performance in San Francisco, Gaga exposed an Ozzy Osbourne T-shirt underneath a black leather jacket, then played his 1980 debut solo single “Crazy Train” as she and her dancers walked a catwalk.

Gene Simmons paid tribute to the fellow rock icon. "Sad to report Ozzy has passed away. He was a giant. Admired and loved by millions of fans worldwide. Prayers and condolences go out to the Osborne family," the KISS rocker wrote, sharing a news link to his death.

Rock royalty is paying tribute to Ozzy Osbourne, who died today at 76.