http://www.youtube.com/atenordelaopera

In November 2009, at the central market in Valencia,Spain, opera singers
dressed as shopkeepers were selling produce at the various stalls there.
Suddenly, Verdi's Il Travatore starts playing over the loudspeakers & they
burst into song. None of the shoppers has a clue what's going on. Sort of
like candid camera but completely charming .