Pierce Brosnan had no idea what the project was about when he signed on. The producers told him it was being filmed in Greece, and Meryl Streep was starring. Brosnan said he would've signed on for anything involving Streep, describing her as "that gorgeous blonde I fancied terribly in Drama School."
Stellan Skarsgård said, "It was absurd to ask me to be in a musical. I can't sing, I can't dance. And then I saw it was also Pierce Brosnan and Colin Firth, and they can't sing and dance either, so I felt a little safer there."
On Inside the Actors Studio (1994), Colin Firth's response to the question "If Heaven exists, what would you like God to say when you arrive at the pearly gates?" was "I personally thought you were very good in Mamma Mia"
Meryl Streep first saw the musical in October 2001 with her daughter Louisa, and her daughter's friends in Manhattan. Streep wrote to the producers to praise them for bringing a little happiness and fun to the lives of New York City's people following the 9/11 terrorist attacks.
The cast members performed their own singing.
Björn Ulvaeus: Composer and executive producer is dressed as a Greek god during the closing credits sequence.
Rita Wilson: The executive producer is dressed as a Greek goddess during the closing credits sequence.