That’s not aerosol in those cans of coif product. It must be helium. What else accounts for “Hairspray,” so bouncy, so bubbly, so buoyant?

This movie musical about the plus-sized white girl who shakes her way onto a segregated teen dance show and brings black high-schoolers with her is a laughing gas.

In 1962 Baltimore where spirits and hairdos soar, the beat is on and outsiders are in. The girl with the highest hair and hopes is Tracy Turnblad (newcomer Nikki Blonsky), observer of three commandments: Gotta-sing, gotta-dance, gotta integrate. Like “Dreamgirls” and “Talk to Me,” “Hairspray” is the Civil Rights era as told through song.

The original “Hairspray,” John Waters’ cheeky 1988 film, was a subversive ode celebrating difference. It begot the 2002 Broadway songfest chronicling the ascendance of teen culture.

For the new film in which a cross-dressing John Travolta appears as Tracy’s XXL-sized mother, Edna, director Adam Shankman plays it relatively straight. His is a generation-gap musical where sunny teens (led by blissful Blonsky and Amanda Bynes) inspire their occasionally shady elders (a miscast Travolta, but wellcast Chris Walken, Queen Latifah and Michelle Pfeiffer) to shed their prejudices and inhibitions.

Shankman, the choreographer-turned-director responsible for the odious “Cheaper By the Dozen II” as well as the guilty pleasure “Bringing Down the House,” cuts this particolored material so that it’s a perfect fit.

The result is a rocking, rollicking crowdpleaser that shakes a tailfeather to Marc Shaiman’s music and smiles along with Scott Wittman’s lyrics, from “Good Morning, Baltimore” where Tracy greets the day, to “You Can’t Stop the Beat” its raise-the-roof finale.

As played by Blonsky, she of the fireplug proportions and the sparkplug energy, Tracy challenges TV station manager Velma Van Tussle (wickedly funny Pfeiffer) to win a spot on “The Corny Collins Show,” Baltimore’s answer to “American Bandstand.” (Corny, played by James Marsden, is a revelation. But then, that could be said about virtually everyone in the ensemble.)

Tracy is colorblind, Velma snowblind: She sees only white. She thinks that audiences (and advertisers) like their teen idols white like the twinkling, winking Link (Zac Efron, best known as Troy in “High School Musical”) and Velma’s untalented daughter, Amber (Brittany Snow). But Tracy cannot be denied.

At first, the teen’s obliviousness to racism and size-ism shields her from the poison darts of Velma’s bigotry. But when Tracy befriends black students (including Seaweed, the terrific Elijah Kelley who stops the movie with “Run and Tell That”) – and picks up some new dance moves – she is a target of discrimination. And as a result joins forces with black deejay Motormouth Maybelle (uproarious Queen Latifah) to protest the station’s discrimination.

Tracy does the stomp, the shake and the locomotion and even gets her agoraphobic mother, Edna (Travolta), as shy as her daughter is gregarious, out of the house.

In the footloose and freewheeling “Hairspray” ensemble where almost everyone is a standout, Travolta is the one misstep.

In his fat suit and harder-than-a-helmet bouffant, Travolta resembles the Sta-Puft Marshmallow Man in a housedress. (His weird attempt at the Bawlmur dialect makes him sound like Mike Myers as Dr. Evil.) Travolta apparently modeled his lumbering-but-dainty performance on one of those tutu-wearing hippos from “Fantasia.”

Thankfully, Travolta’s Edna doesn’t bring down this popsicle-hued dance party. “Hairspray,” which begins as a caricature of separate-but-unequal America, ends in a star-spangled checkerboard. And everybody’s dancing. Even the audience.

3½ stars

Directed by Adam Shankman, written by Leslie Dixon. With John Travolta, Christopher Walken, Michelle Pfeiffer, Nikki Blonsky, Zac Efron, Queen Latifah, Amanda Bynes and Elijah Kelley. Distributed by New Line Cinema.

Running time: 1 hour, 34 mins.

Parent’s guide: PG (suggestive dancing, teen smoking)