Kristine Nielsen is a national treasure. This standout comedic actress has been the best part of any number of stage productions over the last few decades, from Tony-nominated turns in Vanya and Sonia and Masha and Spike and Gary: A Sequel to Titus Andronicus, though she’s been shockingly underemployed on film and TV (despite a key supporting role in HBO’s The Gilded Age as the German-born cook for Christine Baranski’s hoity-toity New York aristocrat).

Nielsen, with her unblinking commitment to absurdity, is the chief reason to see Regretfully, So the Birds Are, a disappointingly underdeveloped farce by Julia Izumi that premiered Tuesday at Off Broadway’s Playwrights Horizons. Here, she’s cast in a supporting role as Elinore Whistler, a suburban New Jersey housewife in jail and awaiting trial after setting fire to her two-timing husband’s den — while he was inside. A former Vicodin addict who seems unrepentant about incinerating her husband of three decades (“may he rest in hell”), she now offers her visiting children the sort of off-kilter advice that could only come from a woman more than a few bubbles off plumb. What elevates Nielsen’s performance is her utter commitment to the role, which she plays not (just) for laughs but with a kind of authenticity that makes us believe this really is just one of life’s true eccentrics, her willingness to resort to homicide just another quirk.

Nielsen also doubles up as a bird, a bossy creature with bright red feathers, and even manages to make this hand-held puppet convincing. Unfortunately, the bird is a central figure in a far-fetched recurring subplot that consumes a lot of the show’s 90-minute running time but achieves little in the way of dramatic payoff.

Sky Smith, Shannon Tyo, Kirstine Nielsen and Sasha Diamond in “Regretfully, So the Birds Are” (Photo: Chelcie Parry)

Izumi’s play is bursting with ideas, and themes, enough to populate three or four plays — or perhaps one lengthier masterwork that ties all the disparate elements together in a more thoughtful, coherent way than she manages to achieve. Instead, we drift from one satirical sketch to another. The burned-alive Whistler patriarch, a clueless Asian studies professor at a New Jersey junior college (Gibson Frazier), has come back as a talking snowman offering advice to his kids.

Those kids, all Asian American adoptees, are itching to search for their birth parents — and the oldest (Shannon Tyo) heads to China and Cambodia because mom could only remember that her adoption involved the letter C. The other two kids (Sky Smith and Sasha Diamond) have sparked up a not-so clandestine romance which only their older sister seems to find objectionable. And the youngest, a principal violist in two symphonies who never seems to spend any time with either one, has used her financial good fortune on the latest splurge of the 1%: buying a piece of the sky as part of the looming “human-to-sky migration.” And that’s just for starters.

If Izumi had focused on one or two of these outlandish ideas, fleshing them out to their logical extremes, she might have produced a more satisfying play equal to her gifts. As it is, we’re left with a scattershot production that careens from moment to moment in ways that can induce mental whiplash.

Jenny Koons directs the shenanigans in the broadest of strokes, and aside from Nielsen the cast all carry a sitcommy vibe that seems less satirical than hokey. The effect becomes all the more troublesome when one of the main plotlines slips into tragedy in the final third — it’s hard to muster much sympathy for characters who never seemed very grounded or real. But like a snowman who’s survived the recently sparse winters of the tri-state area, Izumi has staked her claim as a talent to watch.