Justin Bieber Surprises Rio Fans With Selena Gomez

On My World Tour stop, teen couple share stage for 'Who Says.'

Earlier this year, Justin Bieber hopped onstage with Selena Gomez during a stop on her tour, and on Thursday night, she returned the favor. The couple shared the stage as Bieber performed in Rio de Janeiro, his second night in the city on his My World Tour.

As if debuting his Christmas single, "Mistletoe," wasn't enough of a present for his Brazilian fans, they got the chance to see the teen pop couple perform together. Bieber teased the performance in the hours leading up to his big show, tweeting, "Had a lil fun last night in RIO ... show #2 in RIO is 2nite ... got some very special guests with me 2nite. #Mistletoe." He later added, "Hearing @CobraStarship killing it out there ... almost time RIO ... i got a big surprise tonight. #BRAZIL #myworldtour."

Footage from the performance shows Bieber walking offstage as Gomez comes out to sing her song "Who Says." Toward the end of the song, Bieber returned to sing a few lines, and the pair embraced before Gomez exited the stage.

Bieber later tweeted, "RIO!!! CRAZY!! thanks to @selenagomez for helping me do something special for the crowd. a duet never hurt nobody. WHO SAYS."

OK! magazine reports that Tuesday, the pair was spotted touring the city and taking a helicopter ride. On Wednesday night,

target="_blank">Gomez was photographed backstage watching her boyfriend perform.

Bieber's next tour stop is Sao Paolo. While rocking South America, Bieber announced he's releasing the official version of his single earlier than originally planned: "Thanks to all the love ITUNES is now releasing #MISTLETOE early ... now coming #OCT17th !!! spread the world ... we r going for our first #1!!" he tweeted.

His November 1 holiday album, Under the Mistletoe, will feature appearances from Boyz II Men, Mariah Carey, Busta Rhymes, Usher and the Band Perry.