Time flies when you're a dancing queen. The last time that Anni, Benny, Bjorn, and Agnetha performed publicly together was for British TV in 1982, and aside from an isolated appearance here and there, the crooners responsible for "SOS," "Fernando," "Knowing Me Knowing You" and "Gimme! Gimme! Gimme!"--not to mention a musical Meryl Streep movie--have remained on what was thought to be a lasting break.