Olivier Rousteing, the creative director of Balmain, is too busy to be a bad boy.

The enfant respectable of Paris fashion (who was just 25 when he took over the couturier in 2011) was in New York for barely 48 hours last week, to introduce his new BBuzz Bag at Saks Fifth Avenue.

Wearing a scoop-neck top that showed off his signature pectoral cleft, the young designer presided over a sedate cocktail party Friday night at Le Chalet on the store’s ninth floor. “Leaving tomorrow, arrived yesterday,” he said, with no trace of weariness. “I have to go back to Paris to work on my men’s wear prefall collection and my women’s wear.”

He was also preparing for the release of a documentary about his life, “Wonder Boy,” which debuts this week on French premium cable, ahead of a theatrical release.

“It is about looking for my biological parents and my origin,” said Mr. Rousteing, who was adopted as an infant by a couple in Bordeaux, France. Cameras filmed him 24 hours a day for two years, he said. “But I got used to it.”

A model-heavy crowd came dressed in Balmain looks, with black leather Fonzie jackets on the men and their feminine equivalent draped over shoulders on the women. Tasseled BBuzz bags, which cost up to $2,795, hung demurely at their hips.

The guests, including the scene makers Justine Skye, Olivia Palermo, Noah Schnapp, Sophia Hutchins, Victoria Silvstedt, Sean O’Pry and Princess Olympia of Greece, were as well-behaved as their host. Nobody got tipsy on the complimentary gin-and-tonics, and everybody went outside on the terrace to smoke. Even the dancing felt more like a home school prom than a rowdy fashion party.

Does Mr. Rousteing like to do anything to blow off steam when he is visiting the city that never sleeps? “When I’m here, my favorite thing is seeing friends, and watching movies in their house on Netflix,” he said.

D’accord! But anything else, you know, a little edgy?

Mr. Rousteing shrugged. “That’s it.”

Getting Lost in Chinatown

When Isabelle Huppert, the Oscar-nominated French actress, comes to New York, she is a wild woman by comparison. Her favorite thing to do in the city?

“I like to walk in the streets,” she said Monday night at Metrograph on the Lower East Side. Ms. Huppert had come directly from a flight from Paris to attend a Cinema Society screening of her new film, “Frankie,” a family drama set in Sintra, Portugal.

As it happened, Ms. Huppert got plenty of steps in after the screening. She and her guide got lost walking to the nearby after-party at Hotel 50 Bowery. (Apparently they were relying on G.P.S. driving rather than walking directions, which took them on a circuitous route through Chinatown’s labyrinth of one-way streets)

When Ms. Huppert finally arrived at the Crown, a penthouse space atop the hotel that offers panoramic views north to Midtown, she settled onto a mod sofa in a back corner and received well-wishers and trays of fig-and-ricotta canapés.

Fortunately, her collaborators on the film had plans to spice up her walks. Ira Sachs, the director of the film, said he was going to take her to the Met Breuer to see the Vija Celmins exhibit.

And Marisa Tomei, her co-star, said she invited Ms. Huppert to the Tuesday opening of “The Rose Tattoo,” the play in which Ms. Tomei stars on Broadway.

Guests munching on olive-oil-flavored popcorn included Brenda Vaccaro, Donna Karan, Tory Burch, Harry Benson and Sarita Choudhury. Tyne Daly, the television actress and longtime New Yorker, said she had come to see the film “because it’s free.”

And what’s her favorite thing to do in the city?

“Free films,” she said.