Lady Gaga serenaded old-school crooner Tony Bennett on Sunday night at Roseland Ballroom.

Spies said the “Applause” singer climbed a ladder covered in vines and roses up to a special balcony where Bennett had a front-row seat.

She sang to him, wearing a racy red leotard, ripped fishnets and leather boots.

The pair performed together on Bennett’s 2011 album “Duets II,” and Bennett famously drew a nude sketch of Gaga in a session captured by photographer Annie Leibovitz for Vanity Fair.

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Lady Gaga came out her apartment in blue and white outfit to go to yoga class before her show today in NYC. Pictured: Lady Gaga Ref: SPL727607 280314 Picture by: JDH Imagez / Splash News
This is what Lady Gaga wore to yoga class on March 28. If you expected stretch pants or sweats, you don't know this Lady.Splash News
Caption: Lady Gaga spotted wearing a foil outfit while arriving at her apartment building, after promoting her latest album G.U.Y in New York City. Pictured: Lady Gaga Ref: SPL725323 240314 Picture by: Santi/Splash News
Gaga channeled aluminum foil on her way to her apartment on March 25. Splash News
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Lady Gaga is seen stepping out of her New York City apartment in green mittens. Pictured: Lady Gaga
Gaga's worked with the Muppets before and on March 27, they seemed to have inspired her outfit.Splash News
Lady Gaga steps out in a T-shirt with her father's face printed on it and Hello Kitty shoes at Roseland Ballroom, NYC Date of Picture: 03/27/2014 See the set: SPL726674 Usage: World Rights Caption: Lady Gaga steps out with her father, Joe Germanotta's face printed on her T-shirt and Hello Kitty shoes at Roseland Ballroom, NYC. Pictured: Lady Gaga
Gaga kept her father close to her heart and Hello Kitty on her toes on March 27.Splash News
Lady Gaga leaves Z100 in NYC. Pictured: Lady Gaga Ref: SPL725144 240314 Picture by: BigMediaBoss/Splash News
Gaga says "Artpop can be anything," and on March 24, it was pure bubblegum.Splash News
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Lady Gaga was spotted out in New York City with her usual weird fashion.
Just another day in the colorful life of Gaga.Splash News
Lady Gaga was seen arriving at Roseland Ballroom for rehearsals on Friday afternoon in New York City.
For her birthday on March 28, Gaga wore more layers than most cakes.Splash News
NEW YORK, NY - MARCH 21: Lady Gaga visits the SiriusXM Studios on March 21, 2014 in New York City. (Photo by Jamie McCarthy/Getty Images for SiriusXM)
Gaga looked happy, but serious in all black at SiriusXM studios on March 22.Getty Images
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Lady Gaga coming out of Sirius radio show in NYC. Pictured: Lady Gaga
Gaga's goth inspired look was simple on March 22 — except for the heels.Splash News
Lady Gaga rock a see through outfit coming from rehearsal in NYC Date of Picture: 03/28/2014 See the set: SPL727919 Usage: World Rights Caption: Lady Gaga rock a see through outfit coming from rehearsal in NYC. Pictured: Lady Gaga Ref: SPL727919 280314 Picture by: JDH Imagez / Splash News
Mother Monster gave an eyeful on March 28 when she was spotted leaving rehearsals.Splash News
Lady Gaga covers up in a long, white wig and long off-white fur coat as she leaves the Tracy Martyn Salon on Fifth Avenue / Lady Gaga stepped out in a bizarre outfit yesterday as she arrived at the studio, NYC. Pictured: Lady Gaga / Lady Gaga spotted wearing a pink coat while arriving at The Yoga Spot in New York City. Pictured: Lady Gaga
This is how Gaga does cold weather chic on March 25, 22 and 23.Splash News / Pacific Coast News
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Lady Gaga spotted wearing yellow sunglasses and holding a yellow handbag while arriving at Z100 radio station in New York City. Pictured: Lady Gaga
Gaga looks mostly normal and incredibly lovely on March 24 and 23.Splash News / Pacific Coast News
Lady Gaga did a polar bear-yetti-Christmas ornament look for another grand entrance, as she left her home in a rose covered vintage yellow cab and arrived at Roseland Ballroom for her shut down residence there.
More like Yeti Gaga.Splash News
A fan gave Gaga a dress up doll book of Mother Monster herself on March 26. No word on whether this all-white getup was included.
A fan gave Gaga a dress up doll book of Mother Monster herself on March 26. No word on whether this all-white getup was included.Splash News
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Lady Gaga was seen this evening as she left her first of seven shows at Roseland Ballroom and it was also her birthday so the birthday girl got all done up for her big night. In another space-inspired outfit she wore a sparkly white bodysuit with some extremely interesting shoulder accessories, paired with some pink dinosaur looking heels, and her signature platinum blonde wig that almost touches the floor.
Lady Gaga wore this on March 28. Now that's what we call a birthday suit.Splash News
Caption: 115286, Lady Gaga heads to the studio in her flashy fire-fighter dress in New York City. New York, New York - Saturday March 22, 2014. Photograph: © PacificCoastNews. Los Angeles Office: +1 310.822.0419 London Office: +44 208.090.4079 sales@pacificcoastnews.com FEE MUST BE AGREED PRIOR TO USAGE
Gaga wore this firefighter-meets-ninja garb to the studio.Pacific Coast News
NEW YORK, NY - MARCH 28: Lady Gaga arrives at Roseland Ballroom on March 28, 2014 in New York City. (Photo by Theo Wargo/Getty Images)
Gaga truly blossomed on March 28 outside of Roseland Ballroom.Getty Images
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NEW YORK, NY - MARCH 28: Lady Gaga arrives at Roseland Ballroom on March 28, 2014 in New York City. (Photo by Theo Wargo/Getty Images)
Gaga chose to place a rose in an interesting place on March 28.Getty Images
NEW YORK, NY - MARCH 30: (EXCLUSIVE COVERAGE) Lady Gaga performs onstage at Roseland Ballroom on March 30, 2014 in New York City. (Photo by Theo Wargo/Getty Images)
Gaga's wigs are almost as big as her voice, as evidenced here on March 30.Getty Images
NEW YORK, NY - MARCH 28: (EXCLUSIVE COVERAGE) Lady Gaga performs onstage at Roseland Ballroom on March 28, 2014 in New York City. (Photo by Theo Wargo/Getty Images)
Gaga paid tribute to her Big Apple roots with an F train replica onstage on March 28.Getty Images
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Opening night of Lady Gaga's sold out seven-show run at NYC's Roseland Ballroom, before it closes it doors. Pictured: Lady Gaga
Perhaps mourning the imminent closure of Roseland Ballroom, Gaga rocked a black headpiece for the opening night of her sold out seven-show residency on March 28.Splash News
Lady Gaga performs at Roseland Ballroom, NYC. Pictured: Lady Gaga Ref: SPL727896 280314 Picture by: Rick Davis / Splash News
Gaga somehow made Day-Glo yellow and a keytar look cool on March 28.Splash News
NEW YORK, NY - MARCH 30: (EXCLUSIVE COVERAGE) Lady Gaga performs onstage at Roseland Ballroom on March 30, 2014 in New York City. (Photo by Theo Wargo/Getty Images)
Everything came up roses for Lady Gaga on March 30.Getty Images
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Lady Gaga brung back her famous mermaid look this evening after her show at Roseland Ballroom. After the show she emerged in a big green wig with sea shells and roses throughout, along with floral panties, and bra resembling a sea shell, and she didn't forget her super high heels. She posed for photos with fans and collected a few more belated birthday gifts before heading back home.
At one point outside the venue, Gaga channeled a mermaid ... but with fierce heels instead of a fin on March 30.Splash News
Lady Gaga takes a taxi to Roseland for her third in her series of concerts being held at Roseland in its last week of a long history in Manhattan.
Lady Gaga looked like her old self as she arrived to her final shows at Roseland Ballroom on March 31.Splash News
Lady Gaga and colorful pals were seen arriving at 155 Rivington, formerly St. Jerome's where ex-boyfriend Luc Carl worked as a bartender. The location has reopened under the name Rivington F&B.
Lady Gaga, wearing her sunglasses at night, and colorful pals hit up Rivington F&B after her final Roseland Ballroom performance on March 31.Pacific Coast News
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