Jennifer Lopez attends several parties, but this one was special - the singer surprised her former backup singer Pia Toscano by attending her birthday bash.

The actress surprised Toscano, a former "American Idol" contestant, when she was celebrating her 26th birthday at Crustacean Beverly Hill, by attending the party.

"Pia was shaking when Jennifer walked in the door because she was so excited. She was so touched that Jennifer attended," an onlooker told people.com.

"Jennifer was one of a handful of people that actually brought Pia a gift, and it was the biggest basket in the bunch," the onlooker added.

Toscano was the backup for Lopez when the "American Idol" judge performed her hit single `I luh ya papi` on the Fox reality show last season.

Lopez attended the party with her friend Leah Remini, and the two shared a cocktail with Toscano and chatted the night away in a cabana.

Lopez and her friend left just before midnight, but not before taking a selfie.