Christopher Polk/Getty Images for TASTaylor Swift and Jennifer Lopez brought a little Bronx to Los Angeles last night.
J.Lo was the "22" singer's surprise guest performer during the last stop of her Red Tour at L.A.'s Staple Center.
The two dueted on Lopez's hit, "Jenny From the Block."
Swift introduced Lopez by talking about when she was a little girl.
"You know how you have your favorite song that you just play over and over and over again," she said. "You just blast it in your room and you'd sing in front of your mirror into a hairbrush, right? You have that one favorite song. It was your favorite song to dance to. Los Angeles, this is my hairbrush song."
With that, the sold-out crowd of 15,000 went crazy as they heard the opening notes of "Jenny From the Block."
Lopez appeared at the back of the stage at the top of a staircase wearing a crystal-covered sleeveless shirt and pants along with a matching baseball cap.
The duo sang and strutted around the stage surrounded by Lopez's hunky male dancers.
They ended the number with a big hug before running backstage.
"Thank you for inviting my family to be a part of yours @taylorswift13!!! #RedTourLA," J.Lo tweeted along with an Instagram photo showing four different pics of them in her dressing room.
Another of her tweets reads, "@taylorswift13 had so much fun with you tonight!!! #RedTourLA #jennyfromtheblock #hairbrushsongs."
Swift tweeted, "Sang Jenny From the Block with @JLo tonight at Staples Center. STILL FANGIRLING OUT ABOUT IT."
Just the night before, Judd Apatow and Leslie Mann brought their daughter Maude to see T. Swift in concert. "Leslie and I are so proud of our new daughter @taylorswift13," Apatow cracked on Twitter with a photo of the trio.
Lopez joins a long list of guest performers at Swift's recent concerts. Others include Ellie Goulding, Sara Bareilles, Tegan and Sara, Cher Lloyd and legendary singer-songwriter Carly Simon.