Mamma Mia! Here we go again. My, my, it really does persist, whew. Mamma Mia! It's that show again. My, my, how can this have missed you? In case it somehow has, the indefatigable ABBA jukebox musical makes its umpteenth Chicago stop on its seemingly perpetual (though now non-Equity) tour. It's just here a week, but bye-bye doesn't mean forever.