Every occasion is the right occasion for ABBA. From wistful ballads like “The Winner Takes It All” to uplifting anthems like “Dancing Queen,” the twin vocals of Agnetha Fältskog and Anni-Frid Lyngstad, and the songwriting craft of Björn Ulvaeus and Benny Andersson, have stood the test of time. Now, 40 years after their last public performance together in 1982, the Swedish supergroup has returned with a new album, Voyage, and a new digital show. To celebrate, we look back at their origins, relationships, fashions, hit songs, and pop culture legacy.