Demi Lovato surprised fans by joining the Jonas Brothers during their first show on the Jonas20: Greetings From Your Hometown Tour in New Jersey Sunday.

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Lovato, 32, had previously starred opposite Joe Jonas, 35, in the 2008 Camp Rock film and its 2010 sequel, and the pair performed songs from the movies, including "Wouldn't Change a Thing" and "This is Me," on Sunday.

Lovato and Joe Jonas briefly dated in 2010.

Brothers Kevin Jonas, 37, and Nick Jonas, 32, also appeared in Camp Rock.

Demi Lovato's husband, Jordan Lutes, cheered for his wife from off stage.

"Couldn't be more proud," he captioned a video he posted to social media. "I love you so much baby."

Screenshot via ddlovato/Instagram Stories

The tour celebrates both the group's 20th anniversary and their latest album, Greetings From Your Hometown, which arrived Friday. The album features collaborations with Dean Lewis, Switchfoot and Marshmello, and contains 14 songs.

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"The main thing for us was about telling our stories over the last couple years.... and getting back in touch with our musical roots but also our literal roots in New Jersey," said Joe Jonas on Today Friday.

The tour runs through Nov. 14.

Demi Lovato released a new single, "Fast," earlier this month.