Fans at a New Kids On The Block concert were in for a double delight on Saturday (19Jun10) - when the pop stars brought out the Backstreet Boys for a duet.
The 1980s group thrilled fans at New York City's Radio City Music Hall when they began to cover Backstreet Boys' hit I Want It That Way for the sold-out crowd.
And the audience proceeded to go wild when the Backstreet Boys themselves stepped onto the stage to finish the song with the New Kids.
After the show, New Kid Donnie Wahlberg wrote on his blog, "As for TONIGHT'S Concert.... BACKSTREET BOYS got my respect forever! That was awesome! What a night!... My heart is full."