ABBA's Bjorn Ulvaeus is set to have an incognito cameo in 'Mamma Mia 2: Here We Go Again!'.

ABBA's Benny Anderson and Bjorn Ulvaeus

ABBA's Benny Anderson and Bjorn Ulvaeus

The music of the legendary Swedish pop group - comprised of the 72-year-old songwriter and his former bandmates Agnetha Faltskog, Benny Andersson and Anni-Frid Lyngstad - provides the soundtrack to the sequel, the original movie and the 1999 stage musical upon which both films are based.

Top pay tribute to ABBA's massive contribution, Bjorn appeared as a Greek God at the end of the 2008 movie and he reportedly has a more hidden cameo in the follow-up which only "eagle-eyed fans" will be able to spot.

An insider told The Sun newspaper: "Bjorn is very hands-on with the films. He doesn't want anything to overshadow the main stars or detract from the storyline but for a personal thrill, he loves the idea of being briefly on screen again. Fans will have to be very eagle-eyed to spot him but given he's one of the world's most famous men, he's going to struggle to go totally unnoticed."

The highly anticipated sequel will see the return of Meryl Streep, 67, Amanda Seyfried, 31, Colin Firth, 56, Stellan Skarsgard, 66, Pierce Brosnan, 64, and Dominic Cooper, 39.

'The Best Exotic Marigold Hotel' scribe Ol Parker will be penning and directing the Universal Studios film, while Playtone Pictures, which produced the first installment, has jumped back on board for the forthcoming film.

The iconic musical focused on a bride-to-be Sophie Sheridan (Seyfried) trying to find her real father so that he can walk her down the aisle at her wedding to Sky (Cooper).

But she's in for a shock when she realises that there are three potential men that could be her biological dad.

It's not yet known how bosses plan to push the story on but it's thought they may decide to follow the angle of how Sophie's mother Donna Sheridan (Streep) met the three men; Sam Carmichael (Brosnan), Harry Bright (Firth) and Bill Anderson (Stellan Skarsgard) in the years before the original story takes place.