Madonna isn't one to share the stage with other stars at her shows, but on Tuesday she invited one of the biggest pop sensations in the world to jam during her second night at New York's Madison Square Garden.

No, it wasn't her sometimes rival Lady Gaga.

It was Korean pop explosion Psy, who she flew in from Frankfurt, Germany, for the special honor. According to the Associated Press, Madonna and Psy danced and sang his smash hit, "Gangnam Style," and then took a swing at her song "Music" as well.

Not only did the pair sing Psy's signature tune, but Madonna and her dancers even whipped out the rapper's iconic horsey dance. While Psy shimmied in his red suit, Madonna backed it up into him and then crawled down through his legs, eventually climbing up on his back and riding him like a pony. He returned the favor during "Music" by grinding up on the music icon and clearly having a blast.

She told the crowd that she'd flown her new pal in from Europe that morning and told them that she's a big fan of his. And though he's gone from an obscurity to a world-renowned star signed to Justin Bieber's manager's label, Psy said the Madonna gig topped his list of accomplishments.

In addition to the Psy surprise, Madonna used her time on stage to help collect some money for fellow New Yorkers affected by superstorm Sandy. During "Like a Virgin," fans threw money on stage. She did the same Monday night, pulling in $3,000 for relief efforts.

MTV's "Jersey Shore" cast will also do their part to help out victims of Sandy, particularly those in their homebase of Seaside Heights, New Jersey. They'll be teaming up with the nonprofit organization Architecture for Humanity for "Restore the Shore," a special benefit set to air live at 11 p.m. tomorrow. Fans can text SHORE to 85944 to make a $10 donation.