Phoebe Waller-Bridge will accompany Olivia Colman on the ukelele when The Crown star sings on an album of covers in aid of BBC Children In Need.
The actresses have appeared together in TV shows Broadchurch and Fleabag, but this will be their musical recording debut.
It has previously been revealed that Colman will sing a version of Glory Box by Somerset trip-hop group Portishead for the Got It Covered album, which also includes recordings by Helena Bonham Carter, Jodie Whittaker and David Tennant.
The album is the brainchild of Broadchurch star Shaun Dooley and his wife Polly – and Dooley said he was thrilled when Colman suggested bringing in Waller-Bridge and her sister Isobel to join her on her track.
He told the PA news agency: “We were in the room and Olivia went ‘What if Phoebe played ukele on my track’ and we went ‘yeah’, so she went ‘I will phone her now’.
“Phoebe’s sister Isobel is an amazing composer and musician, she did the music for a play I did, and she came on to play a bit on the Portishead.”
But Waller-Bridge was not the only big star to put in a surprise appearance during the recording sessions for the album.
Dooley was left speechless when he was visited by Taylor Swift while recording a cover of her song Never Grow Up at Abbey Road.
He said: “I am still in a kind of daze about it, if I’m honest.
“The following morning when I woke up, I kind of went ‘That didn’t happen did it?’
“So I had to get my phone out to look at selfies we took just to make sure that actually did happen.”
He said the experience was made even more special because he sings the song, from Swift’s 2010 Speak Now album, to his four children who were there are the time.
He said: “After she came into the studio and we spoke she looked into the balcony where my kids are and she went ‘I will be up in a minute to see you, we will have selfies and things’, she was so lovely.
“Her presence and her demeanour, she just walked into the room and you just feel good about yourself, it’s really bizarre.”
He said he was introduced to the track by his oldest daughter and he now frequently sings it at bedtimes.
“We decided to do this project two years ago. I’m a huge music fan and suddenly the difficulty when you’ve got one song to choose, what song do you pick?
“Immediately it was this song for my kids. I thought about some Elbow tracks, The Verve, Radiohead, The National, and every time I thought about a different track I kept coming back to this, I couldn’t get away from this track.”
However his nerves were tested when he had to sing the track in front of not only Swift, but also Colman and Waller-Bridge.
He said: “Olivia was the second to last one, I was kept til last, so Olivia and Phoebe and Isobel all went ‘We want to stay around for your record to hear you’.
“So I’ve got my wife there, my kids there, all the producers, and I’ve got Taylor Swift, Olivia Colman and Phoebe, all sat looking at me, and it was like ‘This is the most petrifying thing I’ve ever done in my life’.”
Dooley said he was initially shocked by Colman’s choice of song, but said: “When she recorded it at Abbey Road my jaw (hit the floor), you wait til you hear this version, it is unbelievable.
“It is completely Olivia singing but it’s a side of her that you have never heard before, it’s just crazy. It’s dark, it’s sexy, oh it’s brilliant! She’s done cracking job on it.”
The album Children In Need: Got It Covered will be available to buy on November 1, while the accompanying documentary will air on BBC One at 7.30pm on October 30.