‘The 25th Annual Putnam County Spelling Bee” is still very funny and still very sweet. That is the happy news from Circle in the Square, where the show reopened for a Broadway run last night. The musicals content has changed little since its acclaimed off-Broadway run at Second Stage earlier this year. All the things that were right are still right – alas, most of the things that are wrong are still wrong. Fortunately there are more of the former than the latter – many more. Few shows in New York give so much delight.

The real change comes from the venue itself. It had never occurred to me to think of Circle in the Square, Broadway’s subterranean theater-in-the-round, as a high school gymnasium. After this, it’ll be difficult to think of it as anything else. Six little brainiacs and four brave audience volunteers meet for the county spelling bee in a gym decked out with championship banners and anti-bullying slogans, even a fake basketball rim. Director James Lapine and set designer Beowulf Boritt have done a clever, thorough job of transforming the theater.

And not just the theater. The fun now begins before the show does. The theater lobby has been transformed into a high school hallway, adorned with lockers, posters, and elementary school photos of the cast and crew. They’re embarrassing and hilarious: anti-headshots. It’s all a big gimmick, of course. The creative team just wants to soften us up for the goofy adorableness that waits inside. But it’s a good gimmick: I’m glad it softens us up for the goofy adorableness that waits inside.

“Spelling Bee” has taken a long, improbable route to Broadway. It began way the hell off-Broadway, then went to Barrington Stage, then came to Second Stage, and finally landed here, where – in the short, sexy tradition of “Urinetown” and “Avenue Q” – it seems likely to land a Best Musical nomination (at least) from the Tony Awards people. Like their predecessors, songwriter William Finn and librettist Rachel Sheinkin mix ironic laughs and sharp topicality with real affection for their oddball characters. The unacknowledged stylistic granddaddy of all these shows is “The Simpsons.”

The whiz kids here are sometimes cartoonish but never cartoons. The contestants include Chip Tolentino (Jose Llana), the earnest, pubescent Boy Scout; Marcy Park (Deborah Craig), the Asian overachiever trapped in a hell of her own hyper competence; Leaf Coneybear (Jesse Tyler Ferguson), the home-schooled maladroit who makes his own clothes – without much success; and Logainne Schwartzandgrubenierre (Sarah Saltzberg), the junior radical with two overbearing daddies and one overwhelming lisp.

On second viewing, the two characters who stake a slightly stronger claim on our attention are Olive Ostrovsky (Celia Keenan-Bolger), the sweet wallflower in pink overalls, and William Barfee (Dan Fogler), who dresses like a slovenly, globular Angus Young. She maintains a resilient smile and sings like an angel. Her early number, “My Friend the Dictionary,” sets the perfect tone for the night. He spells words with his magic foot, obnoxiously insists that his name be pronounced “Bar-FAY,” and battles valiantly against a sinus condition and raging peanut allergy. So how is it that these two funny little creatures, over the course of a couple of looks, a few flirty interactions, and a wondrous little dance by Dan Knechtges, create the most compelling love story of the Broadway season? It’s a mystery, a joyous one.

Against that triumph has to be weighed certain shortcomings. Even now, after the many iterations between Rebecca Feldman’s original play and the fancy Broadway version, inexplicable weaknesses mar the show. At some point someone hit on the idea of having a parolee named Mitch Mahoney (Derrick Baskin) fulfill his community-service hours by serving as a “comfort counselor” for kids when they lose. It’s an inspired comic premise, all but wasted here.

The same goes for Mr. Fogler’s big number, “Magic Foot.” Here Mr. Lapine and his writers have one of the funniest actors around. (I happened to see Mr. Fogler in a show downtown recently – his comic triumph as Will Barfee is no fluke.) But the number goes nowhere in particular; the lyrics fall flat. A late number for Olive and her parents overstays its welcome, though it is one of the vocal highlights of the night.

Mr. Finn’s music consistently works better than his lyrics, and so does Ms. Sheinkin’s book. There have been plenty of hilarious shows in New York this year, like “Romance,” “Spamalot,” and the late, lamented Dame Edna show. “Spelling Bee” holds its own, laugh for laugh, with any of them. Plenty of credit goes here to Mr. Lapine, who keeps some kind of order over all the silliness; it also belongs to the actors who play the grownups. As hostess and past champion Rona Lisa Peretti and troubled vice principal Douglas Panch, Lisa Howard and Jay Reiss are not just funny in themselves, but the cause of fun in others. As each audience volunteer in turn encountered a carefully tailored putdown, I again found myself wondering: Are they making this up as they go?

As it happens, I caught “Spelling Bee” one night after “Chitty Chitty Bang Bang.” Now there is an instructive comparison. The latter extravaganza dropped seven figures on a flying car prop; the former looks to have spent about four figures on the entire show. (Okay, more than four, but not many.) The most adventurous piece of machinery on the stage of Circle in the Square is a set of bleachers that spins real fast, as long as three or four people push it with their feet. With its loficharm, terrific acting, and irreducible humanity, it’s a credible successor to “Avenue Q.” It lacks some of the inspiration and flair of Marx, Lopez, and Whitty’s show, to be sure. But it offers further evidence that in 21st-century Broadway musicals, size really does matter: Give me small and smart any day.

(1633 Broadway, 212-239-6200).