David Bowie, Gwen Stefani, Iggy Pop: Top 20 music stars' movie cameos

As the latest trailer for upcoming film What To Expect When You're Expecting featuring Cheryl Cole's anticipated cameo is released, we look at the Top 20 music stars' movie cameos, from Coldplay's charitable Chris Martin in Shaun of the Dead to Gwen Stefani's screen siren in The Aviator...