WATCH: Demi Lovato and James Corden deliver telegrams and shave a man's head

It’s carpool karaoke with a twist - introducing singing telegrams.

Dressed in matching gold jackets, yellow scarves and bowler hats, James Corden and Demi Lovato take to the streets of Los Angeles delivering singing telegrams to unsuspecting members of the public.

And it turns out, Demi Lovato is a bit of a laugh.

🎈💥🙈 pic.twitter.com/ls0J1Bwia0

— The Late Late Show with James Corden (@latelateshow) August 5, 2015

“It’s someone’s birthday, someone’s been promoted, and we’re going to go into their place of work; they have no idea we’re turning up; and we’re going to sing them telegrams,” James prepped Demi.

At their first stop they belted out a country number to hairdresser Sarah, who was celebrating her recent promotion from Stylist to Shop Educator.

“And when it comes to blowing people Sarah has no fear,” Demi sings.

It's #SingingTelegrams with @ddlovato and @jkcorden! http://t.co/W9FRhcm2Po pic.twitter.com/atKGGWXTL4

— The Late Late Show with James Corden (@latelateshow) August 5, 2015

The duo then visited office worker Cory to celebrate his 25th birthday, singing: “Mayonnaise is your favourite spread”.

Their final stop was to visit Dr Engel, a dentist who had raised several thousand dollars for the YMCA and after singing an adaptation of the famous song, Demi shaved his head - as you do.