Johnny provided guitar and drums for a cover of Carly Simon's 1972 hit 'You're So Vain', which shock rocker Marilyn felt would be a particularly ''ironic'' track for them to take on.
He told MTV: ''We did a cover version together of a song which we thought was ironic for each other.
''He played drums and lead guitar, and I played guitar and sang.
''It's a bonus track on my record and the video will probably be us looking at each other like a mirror.''
Johnny has previously said he took inspiration from Marilyn for his character Willy Wonka in the 2005 film 'Charlie And The Chocolate Factory'. The pair are friends, and although Marilyn's tracks such as 'Cake and Sodomy' and 'I Don't Like the DRUGS (But The Drugs Like Me)' hardly make him a child friendly performer, he has been booked for his Johnny's son's tenth birthday party.
He added: ''Johnny's son Jack - whose birthday I'm gonna be performing at - was in the room and he actually played on the song too. It's pretty cool.''