Ms Hatcher's plum-coloured dress with lace panels by Jean Paul Gaultier was sheer to the point that the boy-briefs she wore underneath the gown were clearly visible.
Curly hair and strands of pearls completed her wild-girl look.
"The Grammys always push the envelope with fashion and that's what I'm doing," Ms Hatcher said as she went into the Los Angeles ceremony.
Ms Keys chose an Armani Prive black beaded gown with a plunging V-neck and a dramatic low back. It also had a front slit.
"Giorgio Armani made it especially for me. I feel like a winner," Keys told E!'s Ryan Seacrest.
Another sexy number was Christina Milian's silver halter-top Max Azria Atelier dress with a peek-a-boo bodice.
Fashion plate Gwen Stefani's one-shoulder, animal-print gown had a beaded empire waist, a necessary detail to accommodate her pregnant belly.
Strapless gowns a hit
Beyonce was one of the many stars in strapless gowns. Hers was bronze with spider-web beading, which she wore with big, dangling earrings.
Former American Idol winner, Kelly Clarkson's black strapless gown by Max Azria Atelier had a tight bodice and full skirt completely covered in ruffles.
Fergie of the Black Eyed Peas chose a cream-coloured chiffon strapless dress with a bow in the back by Max Azria Atelier
While Fantasia, another American Idol winner, jazzed up her black gown with a giant necklace.
Actress Jenna Elfman was in a metallic patchwork strapless cocktail dress and dangling earrings.
White hot
White was all over the green carpet (sponsor Heineken changed the carpet colour from the traditional red.)
Jennifer Love Hewitt wore almost no jewellery with her white dress.
Ciara had on a sleek white gown with metallic belt by Alberta Ferretti and Mary J. Blige had on a Cinderellalike white halter dress.
The top of Sheryl Crow's black gown was covered with white embroidery.
Male style
Many male stars wore white suits - which dominated the carpet at last year's Grammys, too.
Common said his white suit made him feel "angelic."
John Legend told E! that he chose a white tuxedo because it was his favourite colour.
Ludacris also was in a white suit with a metallic tie.
And rap star, Kanye West paired his white jacket with a red shirt (worn almost completely unbuttoned), black pants and black leather gloves. It was one of seven outfits that Yves Saint Laurent designer Stefano Pilati suggested.
The Game's "accessory" that he carried on his arm was his 2-year-old son. They wore matching black suits, black ties and white shirts.
LL Cool J, who was preparing to jet off to New York after the awards to debut his Todd Smith fashion line, complemented his white suit with a camel-coloured tie and fedora hat.
The English-style grey windowpane suit that Jay Z wore was an attempt "to channel rich businessman," he explained. He wore it with a handkerchief in his pocket and smoky sunglasses.
And with so many different styles at the Grammys, Buddhist monk Lama Tashi, a nominee in the traditional world music album category, fit right in. He wore a red monastic robe that went over one shoulder.