From left, Keegan-Michael Key, Jeremy Shamos, Amy Schumer and Laura Benanti in Steve Martin’s “Meteor Shower” on Broadway. (Matthew Murphy)

With one toe dipped uncertainly in sketch comedy and another in theater of the absurd, Steve Martin’s “Meteor Shower” comes across as oddly, even merrily, flat-footed. Big-time comedians Amy Schumer and Keegan-Michael Key make their Broadway debuts in this lightweight affair, one in which they and co-stars Laura Benanti and Jeremy Shamos do at least manage to give a convincing impression of having a swell old time.

Oh, some cute bits crop up that are tailor-made for Schumer’s brand of socially awkward comedy, and Benanti proves herself dazzlingly right for the role of an inscrutable mischief-maker. As for “Meteor Shower” itself, which had its official opening Wednesday night at Broadway’s Booth Theatre, well, it’s just a weird concoction. Martin is determined in this hour-and-15-minute show to keep us guessing as to where it’s going. The more pressing issue is, you’re never really sure where it’s coming from, either.

The subject is marriage, and a bond tested on an evening in 1993 when the sky is illuminated with a magical rain of celestial objects, and the California home of a milquetoast pair, Schumer’s Corky and Shamos’s Norm, is visited by an eccentrically charismatic couple, Key’s loud-talker Gerald and Benanti’s uninhibited Laura. They’ve arrived, apparently, with the sole intention of throwing curveballs at their hosts, as when Gerald turns back Corky’s invitation to learn more about a topic with the overly snarky retort: “If you don’t mind, I’d rather not. I’ve got a built-in boredom detector.”

The strangeness is trotted out with no foundation; in this sense, “Meteor Shower” is built like a skit on “Saturday Night Live,” Martin’s own longtime proving ground. You can envision the recurring gag: When cast members Key and Benanti knock on the door, a studio audience breaks out into knowing giggles. Yes, time for another installment of “The Uncomfortables,” those outrageous menaces who come for drinks and stay to drive you bonkers! On the night I attended, there was an even surer indication of our being in celebrity-indulgent “SNL” territory: Compelled at one point to curl up and snuggle on a lounge chair, Schumer and Benanti broke character and cracked themselves up.

Amy Schumer, in her Broadway debut, plays uptight Corky. (Matthew Murphy)

Martin is no stranger to theater. His play “Picasso at the Lapin Agile” was produced off-Broadway in the mid-90s, and his musical with Edie Brickell, “Bright Star,” had a short-lived Broadway engagement last year. Like both of those efforts, “Meteor Shower” feels a bit fraudulent, the work of an artist who is sort of patterning off someone else’s easel and can’t quite get it right. With a surfeit of gimmicks under the command of overtaxed director Jerry Zaks — a stop-and-restart plot, a vague supernatural overlay, a set by Beowulf Boritt that needlessly rotates every seven minutes — you’re continually put in mind of a better mastery of surrealism by any one of a range of other dramatists, from Thornton Wilder to Will Eno. 

The plot mechanics are so flimsy that you have to conclude at times that the playwright is having us on: Before we learn the truth about Gerald and Laura, for example, Norm and Corky receive a call from an acquaintance, who briefs them fully on the diabolical rationale for the evening. And if that isn’t plain enough, well, Gerald and Laura eventually explain to us exactly who they are, just so it’s clear to every single person paying up to $350 for a seat to this undercooked event.

Schumer is game enough, though clearly not excessively challenged by playing uptight Corky, who, like the others, isn’t so much a character as a construct. She’s got presence to spare and looks at ease sharing a stage with theater pros like Benanti and Shamos. Key, on the other hand, seems totally at sea. He declaims his lines in a booming voice, as if he’s in a parody of “Macbeth.” As with much else that occurs in “Meteor Shower,” the performance seems to emanate from some other distant planet.

Meteor Shower, by Steve Martin. Directed by Jerry Zaks. Costumes, Ann Roth; lighting, Natasha Katz; sound, Fitz Patton; production stage manager, J. Jason Daunter. About 75 minutes. Tickets: $59-$350. At the Booth Theatre, 222 W. 45th St., New York. Visit telecharge.com or call 212-239-6200.