There’s a difference between a bad performance and miscasting. The former can be redeemed, the latter is insurmountable. A. R. Gurney’s Sylvia a few years ago provided a classic example: This is the story of a happily married middle-aged man who gets a new puppy and discovers that his emotional investment in the dog is destabilizing his marriage. At the height of his infatuation, he sits on the couch and serenades her with Cole Porter’s “Ev’ry Time We Say Goodbye.” At the Manhattan Theatre Club, the pooch was played by Sarah Jessica Parker (pre-“Sex and the City”) and she was awfully cute with her hair pulled in high-tied bunches to suggest doggie ears and her gangly legs romping round the room. With Miss Parker occupying the kennel, the play’s conceit—a pet as sublimated adultery—was plausible.

In London, they cast Zoe Wanamaker—a terrific actress with a much broader ranger than Miss Parker, but twenty years older, less pert, less leggy, less puppyish. None of this is her fault, but certainly her agent and the producers should have seen it: she was about the same age as her middle-aged owner and so at a stroke the visual key to the play—the puppy as affair—was lost, and what was left on stage seemed weird but no longer believable. One of the producers told me that their thinking was that Zoe Wanamaker has a very distinctive face, with an upturned nose and a vaguely canine upper lip, and so they figured she’d