As Oscar hoopla surges, which actress is wearing what designer’s dress on the red carpet will be the raging talk in magazines from In Touch to Italy’s Grazia. Only Rebecca Apsan, lingerie expert and owner of La Petit Coquette in New York City, knows what they’re wearing underneath.

“All the Oscar winners last year were wearing things from us,” she said. “Everyone from Jennifer Connelly to Julianne Moore — who, before every movie, insists on only using our bras — comes in to get fitted by us.”

No longer do only the clothes make the man or woman, but what’s underneath is beginning to have an impact, whether lycra or lace. Café Montmartre will roll out its own red carpet Saturday, not for Oscar, but for its second Underwear Party.

University of Wisconsin Law School student Edward Edney decided to throw his first underwear event at Montmartre last December after he missed his undergraduate years of attending unusual theme parties thrown at Shampoo, the Philadelphia club made famous by this season’s Real World. “I came here and there was no scene for grad students, especially those who had come from the East Coast,” Edney said. “I wanted to bring some of that vibe to Madison.”

Underwear parties got their start in gay clubs. Now, through innovative venues like Shampoo, the trend of showing up stunning in almost nothing has migrated to hetero and mixed clubs on the East Coast. Edney sees it as a way for people to be expressive and sensual in the era of safe sex.

Rebecca, as she is known by regular La Petit Coquette customers such as Sarah Jessica Parker, thinks the obsession with that which leaves more to the imagination is a response to “over-exposure and vulgarity.”

“Young girls are wearing far too little too young. Look at videos and all that ‘stuff’ that’s all over the computer. Lingerie underwear leaves something to the imagination and that can be better than nudity,” Rebecca said.

20 years ago, Rebecca started her shop with her second husband out of passion for light silk disguises. “He used to rip it off my body,” she said.

Ravishment is simply “talking shop” for this 50-year-old bombshell, who insists lingerie has been a key element in her own relationship longevity. That being said, she is proud that the rich and famous don’t just look to her for tips on cotton or lace, but also love.

“An actress, 22 — and I won’t use her name because she’s quite famous — came here because she was having an affair with an older man,” Rebecca said. “She came back and said lingerie changed her love life — sex was explosive.”

One can also see why Rebecca has become the one to call when the Wall Street Journal needs an expert to comment on the craze for special skivvies. Exuding amorous insight, Rebecca, speaking on the reasons her clients are seduced by the now $13-billion-dollar-a-year undergarment industry, isn’t dishing — it’s about strategic planning.

“We’re in the West Village with all the shrinks, NYU professors — they all come here,” she said. “I even have powerful judges who, I can tell you, are wearing air-conditioned silk pieces under those robes.”

The element of only the wearers knowing how sexy they are underneath professional clothes is something that, Rebecca says, makes women feel more driven.

Commenting on the bashfulness of men buying frilly things for women, Rebecca relates a story that shows even larger-than-life men can get skittish. “One day Meryl Streep, Jessica Lange and Sam Shepard came in — no, wait a minute, Sam Shepard waited and paced outside.”

Men looking to buy intimate apparel should, according to Rebecca, “go into her drawers and find her size.”

Edney states that from what he saw at the last Montmartre party, people being out in underwear helped them open up. He expects a much larger crowd for this event and, as a reward for coming almost undressed, free champagne and chocolate-covered strawberries will be served.

Tapping into another “it” thing for the event, DJ Jeremy Thomas will spin Chicago deep house. Toward evidence of the genre reviving, P. Diddy has already released a house song, “Let’s Get Ill,” featuring Kelis and is currently working in Ibiza-based studios.

For a perfect party outfit, La Petite Couqette purchases can be made online at www.thelittleflirt.com. Closer to home, Pink Panties on State Street and the Boston Store are currently having undergarment sales.

Café Montmartre’s Underwear Party begins at 9 p.m. Saturday, Feb. 5. 127 E. Mifflin St., Madison, 53703 — (608) 255-5900.