Cynthia Erivo joins Ariana Grande at London O2 for surprise 'Wicked' duet

Cynthia Erivo joined Ariana Grande on stage at London's 20,000-capacity O2 Arena on August 16, the second night of Grande's 10-show Eternal Sunshine tour run. They performed 'For Good,' from the forthcoming film sequel 'Wicked: For Good,' and a mash-up of 'Get Happy/Happy Days Are Here Again.' The official Wicked YouTube channel posted performance footage on August 17.