George Clooney And Julia Roberts Crash Gwen Stefani's Carpool Karaoke

With the calibre of Carpool Karaoke going up with every episode, the stars are needing to pull out all the stops to stand out above the rest.

And that's just what happened when Gwen Stefani jumped in the car.

The pair were enjoying a few classic No Doubt tunes when James suddenly realised he was late for work and needed to use the carpool lane, which requires four passengers. A few phone calls later and suddenly we have George Clooney and Julia Roberts in the back seat singing along to 'Holla Back Girl''.

"This Sh*t is bananas!".