AceShowbiz - John Legend and Chrissy Teigen surprised fans while filming their upcoming holiday TV special by recruiting singer Meghan Trainor and actress Jane Lynch for an all-star Christmas sing-along.

Jane's fellow former "Glee" co-star Darren Criss and R&B/soul veteran Raphael Saadiq also joined in the fun as they knocked on doors in Los Angeles to serenade members of the public with festive tunes.

Their antics were filmed for "A Legendary Christmas" with John and Chrissy, which is set to air in the U.S. on Wednesday, November 28, and the "All of Me" hitmaker teased the special by sharing a clip of the carolling celebrities on social media.

"This holiday season, we want to celebrate with you," John added in the caption as he promoted the project.

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This holiday season, we want to celebrate with you. Tune in to ""A Legendary Christmas with John and Chrissy,"" on Wednesday, November 28 at 10/9c on @NBC. #ALegendaryChristmas Watch the full caroling video on Facebook

A post shared by John Legend (@johnlegend) on Nov 26, 2018 at 11:34am PST

Wednesday will be a busy night for the singer - he is also set to feature as part of the 2018 Christmas in Rockefeller Center TV celebrations, as the New York City tree is lit up for the holiday season.

However, John has revealed his performance was pre-recorded, after one fan complained about his apparent double booking on Twitter.

"We booked rooms and rented a whip (car) to go see @johnlegend Wednesday in Maryland and now he is most likely going to cancel to host the tree lighting in NY. #DoubleBooked," posted Casey Johnson.

We booked rooms and rented a whip to go see @johnlegend Wednesday in Maryland and now he is most likely going to cancel to host the tree lighting in NY. #DoubleBooked

— Casey Johnson (@cbsfinest540) November 25, 2018

Clearing up any confusion, John responded by reposting Casey's concerned tweet and assured tour ticket holders he would be on the road as planned.

"Have no fear I'll be live in the flesh in Maryland on Wednesday," he replied. "I pre-taped my Rockefeller tree lighting performance on Thanksgiving Eve. See you soon! #ALegendaryChristmas".

DC/MD/VA Have no fear I'll be live in the flesh in Maryland on Wednesday. I pre-taped my Rockefeller tree lighting performance on Thanksgiving Eve. See you soon! #ALegendaryChristmashttps://t.co/BxeEa0FWm7

— John Legend (@johnlegend) November 25, 2018

Both John's tour and TV special are designed to promote his recent holiday album, "A Legendary Christmas", which includes a number of classic carols and festive originals.