Olivia Rodrigo has been covering "Complicated" by Avril Lavigne during all the stops of her Sour tour, but last night was different. During the Toronto show, Lavigne joined her onstage to perform her debut single. The pop star introduced Lavigne as someone “who broke down so many barriers, and opened so many doors for girls like me. I’m so, so, so lucky that she came here tonight to sing with me.” After finishing the song, Rodrigo declared that Lavigne is "so fucking cool." The two have been a dynamic duo for some time now, praising each other at award shows, but this was the first time they performed together. The queen of pop punk commemorated the night with an Instagram post showcasing photos and footage from the night. "Jumped up to sing 'Complicated' on stage with @oliviarodrigo in Toronto tonight," she wrote. "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." See her post and fan-shot footage of the performance below. View this post on Instagram A post shared by Avril Lavigne (@avrillavigne) https://www.youtube.com/watch?vPFSzd2aO-fU&ab_channelShakyShorty In addition to "Complicated," Rodrigo has also been covering Veruca Salt's "Seether" on tour, and the band couldn't be happier. See a full list of Sour tour dates here.