Judas Priest frontman Rob Halford was asked about his brief time fronting Black Sabbath for shows in 1992 and 2004 during an interview with on SiriusXM’s Ozzy’s Boneyard. 

"The first time was in Costa Mesa, in California. I can't remember when. I do know there's an amazing video of the whole show on YouTube somewhere, which sounds good and looks good. That's a great memory.”

"How that happened was… You know, when Ronnie, God bless you, Ronnie [James Dio], was working with Sabbath, and there was an opportunity for the band to do a little bit of a reunion at that show in Costa Mesa with Ozzy, Ronnie said, 'I'm just gonna step aside for personal reasons.' So he did," Rob explained. "And then I get a call from Tony, 'Can you come and help us out?' 'Yeah, what do you want me to do?' Blah blah blah. We talked about the setlist. We put a couple of songs in there that Sabbath hadn't done forever, 'cause they were my favorites and I thought the fans would love 'em. And then the next minute we're doing two shows. We have a bit of a blast in the studio here in Phoenix, bang out the set, and the next day we're playing two sold-out shows in Costa Mesa. So that was amazing.

"And then you go forward. And this is just what we do for each other in bands. Ozzy wasn't feeling too well with his throat, and I get a phone call from Sharon [Osbourne]… And the same deal. 'He's got this bronchitis thing. Can you step in for the show? 'Yeah, sure. Which one?' 'Tonight.' I'm, like, 'Tonight?' 'Yeah. Can you do the show tonight?' So I did. I did the Priest set, had a shower, got changed, ran out and did the Ozzy thing with Sabbath. So that's happened two or three times.”