During his pit stop in South America, where he performed in Argentina with his "One on One" Tour, Paul McCartney was in for a real treat! In his concert Wednesday night at the Estadio Ciudad de Plata in La Plata, McCartney was joined on stage by a young girl, her mom and her teddy bear. What started off as a sweet fan moment later turned into a jam session.

"What is your name?" asked McCartney in front of the sold-out crowd. "Leila," responded the young girl. Her mother, Mariana, also introduced herself. The family traveled from Buenos Aires to La Plata to catch their idol in concert. 

"What do you want to do? You want me to sign your doll?" asked McCartney. Although the idea sounded great, the young fan denied the autograph and instead had another proposal for the English singer-songwriter. "I want to play the bass with you," she said. "This could be interesting. O.K., I didn't see this coming," said McCartney. "You want to play bass with our band?" he asked as one of the band members handed Leila a white bass.

With chants and applauds, the crowd quickly approved and the two performed an improvised version of The Beatles classic 1969 single "Get Back." "What do you think of that?" asked the 73-year-old musician after performing and singing with the talented Argentine girl. 

For those who missed this once-in-a-lifetime moment, McCartney later tweeted a photo for his nearly three million followers to enjoy. "10-year-old Leila has wish granted, playing bass with Paul onstage in Buenos Aires #OneOnOne," shared the iconic artist on Twitter. 

McCartney's "One on One" tour embarked April 13 with nine concert dates in the United States. From May 15 - 19 he was in Argentina before parting ways to Europe, where he will perform shows from May 28 to June 30. McCartney will then return to North American for a 17-day  concert beginning July 8 in Milwaukee, Wisconsin, and ending October 15 in Indio, California.