Context: Mamma Mia! (promoted as Mamma Mia! The Movie) is a 2008 jukebox musical romantic comedy film directed by Phyllida Lloyd and written by Catherine Johnson based on the 1999 musical of the same name, also written by Johnson, which itself is based on the songs of pop group ABBA, including the title song, with additional music composed by ABBA member Benny Andersson. The film features an ensemble cast, including Meryl Streep, Pierce Brosnan, Colin Firth, Stellan Skarsgard, Julie Walters, Dominic Cooper, Amanda Seyfried and Christine Baranski. The plot follows a young bride-to-be who invites three men to her upcoming wedding, each one with the possibility of being her father. The film was an international co-production between Germany, the United Kingdom, and the United States, and was co-produced by Relativity Media, Playtone and Littlestar Productions.

Question: when did the original mamma mia come out?
Steam of consciousness below:
To answer this question, we should know that: The Movie ) is a 2008 jukebox musical romantic comedy film directed by Phyllida Lloyd and written by Catherine Johnson based on the 1999 musical of the same name, also written by Johnson, which itself is based on the songs of pop group ABBA, including the title song, with additional music composed by ABBA member Benny Andersson.
So, the answer is 1999.