Jen Silverman’s The Roommate has the all the makings of an old-fashioned theatrical boulevardier, the sort of middlebrow comedy that used to dominate Broadway in the era of Neil Simon. The comparison is apt since in many ways this is a distaff version of Simon’s 1965 hit The Odd Couple, in which two slightly past middle-aged singletons of very different backgrounds and temperaments decide to shack up together for reasons that seem forced but that are integral to the plot (such as it is). The laughs come sporadically but consistently, but the chief draw of this two-person one-act is the stunt casting of Patti LuPone and Mia Farrow, the latter returning to Broadway for the first time in a decade. (Director Jack O’Brien smartly dispatches with the customary entrance applause up front, with their names projected on the back wall, before they walk off again to begin the play properly. )

Farrow, naturally, plays the Felix Unger of the pair — a primly uptight Iowa woman who seems at a loss on how to fill her empty-test days beyond her Thursday combo of book club and shopping. Her son is a fashion designer in New York City whom she insists is not gay (despite multiple clues that he might well be) and whom she leaves meandering, smothering voice messages that indicate just why he was so eager to leave the nest. For some reason, she’s decided to welcome a roommate — not for the money, she states, though the rental income is an added bonus. Perhaps she needs to pay off the no-doubt recent remodel of her home, designed by Mikaal Sulaiman with an abstract framework and a kind of interior Scandinavian chic that seems far too hip for its owner. (There’s not a hint of gingham or ruffles or country-kitchen.)

LuPone’s Robyn blows into Sharon’s unassuming Midwestern home like a tornado — she’s a brash, leather-jacket-wearing broad from Queens who quickly establishes her rebel bona fides when she reveals herself as a gay, vegan former potter and slam poet who smokes (and grows) cannabis. Her assertiveness also allows her to deflect attention from a personal backstory that she holds close to her vest, including the reason she was so quick to escape New York and what sort of family or career she left behind there.

It’s an intriguing set-up, and you can see how Farrow’s very sheltered Sharon might open up in the presence of this dynamic outsider while retaining her Midwestern sensibility. When Robyn pours her almond milk in their morning coffee cups, Sharon barely disguises her cringing dislike and dumps the contents into the sink — but only when Robyn’s back is turned. In another memorable moment, Farrow slowly spins in place at the kitchen counter when taking her first puff of a joint, like a schoolgirl counting deliberately in a game of hide-and-seek, and then states matter-of-factly: “I don’t feel anything.”

Before long, Sharon is feeling a lot — and she’s shucking inhibitions as easily as she would an ear of Iowa corn. Silverman has planted the seeds for this closet subversive with some unexpectedly sarcastic asides that Farrow delivers early on in a Midwestern tone so flat that the bite barely registers. Take this dig on locals in a hot yoga class: “They all look so healthy and happy, you sort of want to injure them.” What initially seems an out-of-character jab emerges as foreshadowing of Sharon’s willingness, perhaps even eagerness, to become the “bad girl” she’s never dared to be. LuPone has the louder, flashier role here, but it’s Farrow continually who grabs our attention with her character’s more soft-spoken transformation.

There are limits to Sharon’s outlaw evolution. After all, this is the sort of Chekhov-defying comedy that introduces a Walmart-purchased shotgun that does not go off before the final curtain. Because how could you kill off national treasures like Farrow and LuPone — or risk audience good will by turning them into murderers? You will no doubt see where the tea-towel-thin plot is going long before the characters do — but then part of their appeal is that they’re both well-meaning but a little dim. Still, in the hands of pros like Farrow and LuPone, they manage to glisten just a little bit brighter than the script demands.

THE ROOMMATE
Booth Theatre, Broadway
Running time: 1 hour, 40 minutes (no intermission)
Tickets on sale through Dec. 15