JC Chasez Duets On 'NYSNC Song With Matthew Morrison In London

Former 'NSYNC member JC Chasez made a surprise appearance and his friend Matthew Morrison's London concert last night, joining the 'Glee' star on stage for a duet of the boyband classic, "This I Promise You."

Morrison, who toured London in support of his recently released self-titled solo effort, will open for the Backstreet Boys and New Kids On The Block tour in the U.S. in July.

Chasez also took to the stage for a solo rendition of Journey's "Don't Stop Believing."