Olivia Rodrigo took the stage with Billy Joel on Wednesday night at his Madison Square Garden concert to sing her hit song "Deja Vu" and Joel's classic "Uptown Girl." 

Rodrigo's song "Deja Vu" references both Joel and his 1983 song with her lyrics "I'll bet that she knows Bill Joel/'Cause you played her 'Uptown Girl." Rodrigo got to sing the lyric with Joel playing the piano behind her on the MSG stage. 

After performing, Rodrigo took to Instagram to celebrate the moment. 

Olivia Rodrigo and Billy Joel singing at Madison Square Garden

Olivia Rodrigo joined Billy Joel on stage at his MSG concert to sing "Deja Vu" and "Uptown Girl."  (Kevin Mazur/Getty Images)

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She first posted a video to her Instagram story of her view in the crowd at the show with the caption "I sang with Billy Joel at Madison Square Garden today are you kidding." 

She also posted a picture of her and Joel to her Instagram story, a video of her singing the iconic Billy Joel line from "Deja Vu," and a selfie of the two which she captioned "biggest honor ever still crying thank u Billy!!!!!!!"

This show marked Joel's 82nd show at Madison Square Garden. He started his residency at MSG in 2014. 

Olivia Rodrigo and Billie Joel on stage

Olivia Rodrigo sang her hit song "Deja Vu," which makes reference to Billy Joel.  (Kevin Mazur/Getty Images)

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The "Piano Man" singer also posted to his Instagram with pictures of the two up on stage together. 

"Good 4 u if you made it to @thegarden tonight! @oliviarodrigo hit the stage as Billy Joel's surprise guest," he captioned the photo. 

Olivia Rodrigo and Billy Joel

Olivia Rodrigo also sang a duet of "Uptown Girl" with Billy Joel.  (Kevin Mazur/Getty Images)

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Rodrigo's appearance at MSG comes after her own "Sour" tour, which wrapped up in July.