The crossword solutions for the term 'Mamma Mia! Foursome' are EMS (3 letters) and ABBA (4 letters). EMS stands for Emergency Medical Services, which is a service that provides medical care in emergency situations. ABBA is a Swedish pop group from the 1970s, known for their hit songs such as 'Dancing Queen' and 'Mamma Mia'. The term 'Mamma Mia! Foursome' refers to the four members of ABBA, who were Benny Andersson, Björn Ulvaeus, Agnetha Fältskog, and Anni-Frid Lyngstad.