She didn't want an autograph after all. She wanted to jam with her favorite singer.
And so she did.
Ten-year-old Leila Lacase was in the audience this week with her mother at Paul McCartney's sold-out show at La Plata Stadium in Buenos Aires. She was holding up a poster that asked the Beatles legend to sign her stuffed animal.
So the famous left-handed bass player brought the girl and her mom onstage. He leaned down and asked if she wanted his signature.
She wasn't having any of it. "I want to play the bass with you," the little girl said, pronouncing the name of the musical instrument like the name of the fish.
Taken aback, McCartney laughed and observed she didn't have a "bass" with her, mimicking her pronunciation.
Lacase pointed behind him, where a gleaming white bass sat onstage.
To raucous applause, a roadie walked out with the bass and hung its strap over her shoulders. The instrument dangled above her feet, but that didn't stop her. "I didn't see this coming!" McCartney shouted.
And he ripped into "Get Back" from the Beatles' hit "Let It Be" album, and Lacase plucked right along, nodding her head in time with the beat.
McCartney lowered the microphone so she could sing along. She knew every word.
"What do you think of that?" the knighted McCartney crowed to thunderous cheers. After kissing Sir Paul, she leaned into the mic and said, "Muchas gracias."
And that was how a little girl held her own while onstage with rock royalty.
And yes, video of the performance is going viral, with more than 200,000 views on YouTube and thousands more on Facebook and Twitter.