Early trailers show Cher being referred to as "Grandma" by Amanda Seyfried and is therefore, presumably, playing Donna's (Meryl Streep's) mother. Cher is just three years older than Meryl Streep.
Cher was originally offered the role of Tanya in the first film which she turned down. She appears in this movie but in a different role.
Although Cher began in music and is better known as a musician these days, this will only be her second appearance in a musical following the under performing movie Burlesque (2010). It also marks the first sequel she has appeared in.
The film choreographer is the same choreographer who worked with the traveling Mamma Mia North American Farewell Tour.
The trailer sets Donna's pregnancy in 1979, which sets Mamma Mia! (2008) around 1998.
This film marks the second film collaboration between Cher and Meryl Streep, the first being Silkwood (1983). They were also in Stuck on You (2003) together where Meryl Streep made an uncredited appearance in the movie.
Stellan Skarsgård, Jeremy Irvine and Colin Firth also co-starred together in The Railway Man (2013), where Irvine played the younger version of Firth's character. In Mamma Mia! Here We Go Again, Irvine plays the younger version of Pierce Brosnan's character.
Cher, who is playing Sophie's grandmother in this movie, had a cameo in ABBA's last video in 2004, named ABBA: Our Last Video Ever (2004). The video was released due to ABBA's 30th anniversary since the winning of the Eurovision Song Contest of 1974. In the video, Cher was an audience member while ABBA, portrayed by puppets, performer their winning song "Waterloo."
Hugh Skinner and Amanda Seyfried both appeared in the 2012 film Les Misérables with Skinner playing Joly and Seyfried playing Cosette.
Lily James and Stellan Skargaard previously acted together in Cinderella, but they do not share any scenes.
ABBA member, Björn, makes a cameo appearance in the number "When I Kissed The Teacher".
Second collaboration between Colin Firth, Jeremy Irvine and Stellan Skarsgård. First was The Railway Man which was released in the spring of 2014.
Benny Anderson will appear as a University Chancellor during young Donna's Graduation. Benny Anderson is one of the members of the ABBA which the musical is based on.