It’s a wonder that it’s taken this long to cast the irrepressible Sutton Foster in that old high school and community theater staple Once Upon a Mattress, the 1959 chestnut from composer Mary Rodgers and lyricist Marshall Barer that has lingered in the repertory as a witty send-up The Princess and the Pea fairy tale for decades. Foster proves she has the comedic gifts to shine in the role that made Carol Burnett a star, from her expressive facial expressions to her off-kilter line readings (and mid-song vocal inflections). She also boasts once-in-a-generation gifts as a dancer — here eschewing her tap skills to deploy her lithe limbs for physical humor, striking acrobatic poses (and the full splits) atop that 20-mattress bed in a vain effort to find a comfortable position.

Foster’s performance in director Lear deBassonet’s delightful revival, which opened Wednesday for a two-week run at the Encores! series at New York City Center, is a triumph of clever casting — and she’s matched by co-stars who are every bit as gifted and match their leading lady with infectious onstage enthusiasm.

Foster’s Princess Winnifred the Woebegone, an unrefined royal from the nearby swamp, has arrived in a medieval kingdom whose ruling monarch (played by Harriet Harris, with hilarious hauteur) has thwarted her son, the foot-stompingly immature Prince Dauntless (Michael Urie, a convincingly expressive man-child), from marrying — and thus ending her rule. (There’s a quasi-feminist angle to her motives here, one that gets a boost from Amy Sherman-Palladino’s updated adaptation of the original book by Barer, Jay Thompson, and Dean Fuller.) After rejecting 12 potential princesses on a series of ever-more-outrageous pretexts, Harris’s Queen Aggravain seems especially alarmed by the arrival of Winnifred, a guileless outsider who immediately captures Dauntless’s eye, and threatens both Aggravain’s rule and the kingdom-wide moratorium on marriage.

There are others rooting for the couple, too. Maid-in-waiting to-be Lady Larken (the crystal-voiced Nikki Renée Daniels) has gotten pregnant by her dimwitted knight beau Sir Harry (Cheyenne Jackson, in sweet himbo mode) and needs Dauntless to wed to get hitched herself and preserve her honor. Also conspiring to end the queen’s schemes are the mute king (David Patrick Kelly, going full panto) and the fabulous narrator/court jester (J. Harrison Ghee, in fine voice and even finer duds, designed by costumer Andrea Hood). The songs, which display Barer’s flair for internal rhymes and worldplay, are an absolute delight — and Winnifred’s ironic opening number, “Shy,” recalls Foster’s similarly perverse showstopper from The Drowsy Chaperone, “Show Off,” where she insisted she didn’t want to show off in increasingly show-offy ways. (Lorin Latarro’s choreography has a swagger without ever going over the top.)

It’s a pleasure to hear Rodgers’s melodic score played by a lush 26-piece orchestra, here under Mary Mitchell-Campbell’s baton. Despite the speedy 10-day rehearsal period, the cast has gelled to an almost miraculous degree by Wednesday’s opening night. Foster and Urie spark with a kind of middle-school first-crush chemistry, full of sidelong glances and shoulder punches, that is both charming and convincingly apt for the material.

Still, there are some lulls and repetitions here, particularly in the first act — one wishes that deBassonet and Sherman-Palladino (who eliminated the original Minstrel character and combined his lines and songs with the Jester’s) had been even more ruthless in paring down some of the redundancies of the original script. We all grew up on fairy tales, and don’t need all the reminders of where the plot is headed. But this production proves just how sturdy an entertainment Once Upon a Mattress remains — many of the biggest laughs are now 65 years old, and show no need for retirement. This is just good, old-fashioned fun.