The singer and Idol alum – who surprised fellow alum Diana DeGarmo with a proposal on the American Idol finale last year – shocked her again in Las Vegas on Friday.
DeGarmo, 25, was celebrating her bachelorette party with the Chippendales at the Rio All-Suite Hotel and Casino, when Young, 32, made a guest appearance on stage.
"I can't believe Ace surprised me again," DeGarmo tells PEOPLE. "I am so beyond lucky to have my best friend always keeping me on my toes no matter where we are."
"Ace is the sexiest man alive so he fit in perfectly with the Chippendales," says DeGarmo. "He also rocked that bowtie and cuffs like nobody's business. He might have another calling in Vegas one day!"
As for Young, he was just happy to see his fiancée's reaction.
"I brought "Sexy Back" and wore my "Suit & Tie" to surprise the love of my life," he jokes to PEOPLE. "I would do it 100 times more just to see that look on her face!"