Popsugar Entertainment Mamma Mia 2 Mamma Mia! Here We Go Again New Cast Members See the Original Mamma Mia! Cast and Their Younger Selves, Side by Side 17 July 2018 by Kelsie Gibson View On One Page Photo 4 of 6 ADVERTISEMENT () Start Slideshow Share This Link Copy ← Use Arrow Keys → 4 Alexa Davies and Julie Walters as Rosie The 23-year-old actress, of Harlots and Grantchester fame, will play Rosie in flashbacks. Previous Next Start Slideshow Mamma Mia 2MoviesMamma Mia