Television fans know her as as Cristina Yang from Grey’s Anatomy and Eve Polastri in Killing Eve. In an audacious departure, Sandra Oh now descends on the Metropolitan Opera as the Duchesse de Krakentorp in Donizetti’s feather-weight comedy La Fille du Régiment. She’s following in illustrious footsteps. In the 1980s, three decades after setting the Met on fire as Salome, the Bulgarian bombshell Ljuba Welitsch made a comeback as Krakentorp. In 2010, three decades after warbling “Let the bright seraphim” to a TV audience of 750,000 from Charles and Diana’s wedding, Kiri Te Kanawa took a crack at it, too, notching more performances than in signature roles like Desdemona, and the Marschallin. Some will call the part a nothingburger. True enough, she enters only some nine minutes before final curtain, speaks little, and sings not a note. But she decamps with a howl not unworthy of Medea. In 2008, when Laurent Pelly’s current production was new, the Broadway legend Marian Seldes showed what a pro can do with such material, as you can see for yourself on the Met’s streaming platform. But really, the opera belongs to the singers. In the current revival, the stars warming up the house for Oh’s cameo are Erin Morley as the supposed orphan raised from infancy by a company of soldiers and Lawrence Brownlee as the Tyrolean lad who saves her from falling off an Alp. From Morley, expect, for starters, cascades of crystalline coloratura; from Brownlee, for starters, a rapid-fire volley of nine high C’s and a possible encore. —Matthew Gurewitsch