Ms. Rebeck’s last New York offering, Mauritius, which played on Broadway two seasons ago and was also very funny, although much darker and tenser—no relaxation there!—was set in the cloak-and-dagger world of duplicitous philatelists.

With The Understudy, which opened a week ago at the Roundabout Theatre Company’s Off Broadway space, the Laura Pels Theatre, she’s in more familiar theatrical territory. The Understudy is a backstage comedy, and it’s about three of those lonely cogs.

Harry is a frustrated and bitter actor who has been cast as an understudy in the Broadway transfer of a successful and movie-star-driven production of an apocryphal long-lost Kafka play. He’s sarcastic and snide and contemptuous of the stars, especially the one he’s understudying, who has just released a blockbuster action flick in which his main obligation, according to Harry, is to yell “Get in the truck!” with gravity and intensity and taut pecs.

Jake is that action star, who is both convinced he’s a big deal and frustrated he’s less important than the play’s main star, the absent Bruce, who makes $22 million per picture (Jake got only $2.3 million for his action film).

Finally, there’s Roxanne, the super-competent stage manager, who, it turns out, was engaged to Harry until he left her, not quite at the altar but very close to it. She’s trying to get through this rehearsal, managing Jake’s ego and Harry’s petulance and an unseen stoner stagehand who consistently runs the wrong cues.

Julie White plays Roxanne, and it’s impossible not to adore her. (It is, I suspect, impossible not to adore her in anything. When she won her Tony Award for Little Dog Laughed three years ago, she left me less impressed with the play: If she could render a mere acceptance speech so memorably hilarious and moving, who’s to say Douglas Carter Beane’s script was necessarily any good?) She’s funny, as always, but here she’s also convincingly hurt and angry.

Justin Kirk, best known as the devilishly lovable brother-in-law Andy on Weeds, is Harry, and he brings a similar sarcastic charm to this role that he does to his TV character. That persona can grow just a touch grating—one must have affects other than snide, no?—but there’s real chemistry, based on a shared sarcastic sensibility, between him and Ms. White.

It’s hardest to judge Mark-Paul Gosselaar, who is beloved by a generation—my generation—as Zach Morris, the troublemaking popular kid of Saved by the Bell’s Bayside High. Somewhat stiff and often obviously emphatic, is he a good actor playing a bad actor, or is he a mediocre actor doing his best? In truth, either way works, which might be the mark of perfect stunt casting.

There’s some convenience to the script. If Jake thinks he’s too big a star to be understudied by a nobody like Harry, why is he simultaneously understudying for Bruce? (It provides a setup for the two of them to be at rehearsal together, but it doesn’t quite make sense.) It’s tough to tell whether we’re supposed to think the Kafka script they’re rehearsing is any good—the few lines of dialogue we hear from it aren’t, and we’re supposed to take it as a joke each time Jake starts speaking rapturously of Kafka’s genius (the character is a dolt who thinks he’s smart), but then, the two smart characters seem impressed by the play, too. And while I can accept the characters’ regular bathroom breaks and forgotten hand props to get one or another offstage for a tête-à-tête between the other two, don’t you think eventually they’d remember the fictional theater’s intercom system and stop revealing secrets that their offstage colleagues inevitably overhear?

But those are small quibbles. It’s a fun night at the theater. Near the end, after all that’s gone wrong—moving sets, broken relationships, fights—Jake and Harry have been preparing to rehearse a big dance scene. There’s one more bit of bad news, but, like Peggy Lee in that song, they just keep dancing. It’s a funny ending to a funny play, and not a bad outlook on life, either.

I WISH I could tell you something about what happens in Idiot Savant, the latest spectacle from the experimental playwright Richard Foreman, which opened last week at the Public Theater. But I can’t; despite sitting through it and reading the script, I have no idea.

This is apparently all right, however, and may be the point: “I defy you to try to give a synopsis of any of Foreman’s plays,” writes Oskar Eustis, the Public’s artistic director, in a note in the Playbill. O.K., Oskar, you win.

But Mr. Eustis goes on in that note to write of the “moment to moment delight” of watching Mr. Foreman’s work, and that’s where I must disagree. I know I’m supposed to like this play, supposed to appreciate Mr. Foreman’s bold genius, supposed to be awed and impressed by the nonsensical goings-on, and I’m aware that my lack of appreciation for them marks me only as a philistine. Still, I was entirely undelighted.

That’s not quite fair; I was only mostly undelighted. Mr. Foreman writes, designs and directs his shows, and the design, at least, was a sight: Enormous upstage Victorian-ish walls, covered with patterns and portraits and mirrors and gingerbread; small crystal chandeliers hanging over the stage and house; actors in stylized samurai-meets-Victorian outfits; all manner of unusual props, from imitation rowboats to bows and arrows to a fake duck, all itemized by a voice-of-God voice-over at the play’s start. And Willem Dafoe gives an intense, controlled performance as the titular Idiot—it is unclear what exactly he’s doing, of course, but he does it very well.

It’s all interesting, at least, if not precisely enjoyable—at least until, yet again, the bright floodlights over the stage go on, pointed into the audience’s eyes, while a recording plays sirens blaring and telephones ringing and an amplified woman’s piercing voice shouts “Watch out!” That’s when I decided I was envious of the man seated next to me, in a suit of leather: He was somehow sleeping through it.

editorial@observer.com