Olivia Rodrigo fans were transported to the early aughts when the singer brought Avril Lavigne onstage for a surprise duet of "Complicated."

The "Driver's License" singer was in Toronto as part of her Sour Tour on Friday, when she introduced the punk sensation before launching into a performance of the 2002 hit. "I'm so, so, so lucky because she came here tonight to sing with me," said Rodrigo, as the overjoyed crowd erupted with applause. "Please give it up for Avril Lavigne!"

The 19-year old and the Canadian born Lavigne wore similar looks that included plaid pleated skirts and black boots.

Following the show-stopping moment, Rodrigo shared her excitement in a post on Instagram.

"Toronto last night was special thank u dearest @avrillavigne for singing with me. look up 2 u so much," she captioned an image of the pair.

Lavigne also commemorated the moment on the platform, writing: "Jumped up to sing 'Complicated' on stage with @oliviarodrigo in Toronto tonight," she wrote on Instagram. "It was very sweet to perform with you tonight on your SOUR tour!! Have an incredible tour gurl. Keep killing it. Sending you so much love."

The Grammy-nominated "Complicated" served as Lavigne's debut track and the first single off of her album Let Go and became an anthem for many young people at the time. At the time, Entertainment Weekly's David Browne noted, "Avril Lavigne's not kidding about that title, she's the epitome of the blossoming anti-Britney movement."

Rodrigo has been covering the song over the course of the tour, which is set to continue with dates in the U.S. and Europe running until July.

The star shared her adoration of Lavigne last year when the 37-year-old presented her with the "Songwriter of the Year" award at the Variety Hitmakers event.

"I'm such a massive fan of you. I look up to you so much," Rodrigo shared.

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