Actress Rooney Mara arrives at the 84th Annual Academy Awards...

Actress Rooney Mara arrives at the 84th Annual Academy Awards held at the Hollywood & Highland Center in Los Angeles. (Feb. 26, 2012) Credit: Getty Images

Double-stick tape may have been the accessory du jour at the 84th annual Academy Awards last night as more than a few red carpet stars wore seriously plunging necklines.

Most uncomfortable, perhaps, was Rooney Mara in her deep-V white Givenchy. Pundits saluted her for breaking out of her "Dragon" girl black, but she kept checking to make sure all was in place. Viola Davis -- killer in emerald, body-hugging Vera Wang that ended in a plume of ruffles and pleats -- also showed some serious décolletage. And natch, Jennifer Lopez went really deep, too, in a barely there Zuhair Murad that may have needed a bit more tape during her onstage presentation. Yikes!

But even if the gowns weren't plunging, most of the ladies were giving Oscar the cold shoulder. From gamine Michelle Williams' coral stunner -- a chiffon ruffled, strapless Louis Vuitton with a peplum -- to the swath of metallic satin by Marchesa that encased Stacey Keibler, shoulders were predominantly bare.

Natalie Portman wore a strapless, polka dot, red vintage haute couture Christian Dior number from 1954 -- very Grace Kelly. Jessica Chastain was positively regal in Alexander McQueen's black-and-gold embroidered confection. Gwyneth Paltrow topped her one-shoulder Tom Ford jersey slither with -- a cape. Likewise, Glenn Close, bombshell in strapless hunter green Zac Posen tossed a jaunty matching tuxedo jacket over her shoulders.

Finally, red carpet queen Angelina Jolie wore Versace's strapless asymmetrical gown with a daring, thigh-high slit.

Some opted for more cover, including best supporting actress winner Octavia Spencer, perfect in a shirred, white, sparkling Tadashi Shoji with capped sleeves. But covered didn't always work: In a rare miss, 20-year-old Shailene Woodley looked too grown up in Valentino couture.

As for the guys, it was tuxes as usual, save for Sacha Baron Cohen, who wore a "dictator's" uniform by, he said, John Galliano. Poor Ryan Seacrest wore pancake mix on his Burberry tux after the comedian pranked him. Seacrest, always prepared, had another jacket on hand.

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