(Gibson) Ozzy Osbourne had a pair of unlikely guest vocalists on his 1988 album No Rest for The Wicked: Howard Kaylan and Mark Volman, better known as Flo and Eddie from Frank Zappa's Mothers of Invention and The Turtles (of "Happy Together" fame).
In the second part of his long-ranging interview with Bravewords.com, bass player Bob Daisley said Flo and Eddie sang background vocals on the album, for which Daisley wrote the lyrics. No Rest was Ozzy's first album with Zakk Wylde on guitar.
Daisley also discussed his Living Loud band with guitarist Steve Morse, vocalist Jimmy Barnes (who was once a contender for Van Halen) and former Ozzy bandmate Lee Kerslake. Daisley said an early plan for a collaboration with Kerslake was a Randy Rhoads tribute involving a rotating roster of guests including Brian May, Gary Moore, Deep Purple keyboard players Jon Lord and Don Airey and, in an interesting twist, Ronnie James Dio on vocals. more on this story