bag through the wind ♪ >> that's katy perry's big hit "fireworks" and the 900 students of the simpson valley middle school. >> the video is the idea of one teacher who worked with these students for three weeks. coriographing the whole thing. the principal gave everyone an hour to get it done on tuesday. >> they got it done in just two takes and say it's a great builder of school spirit. nicely going. >> i want to do one of those flash mob things. we should do a "world news now" flash mob something. >> let's get real. >> ain't enough diet coke in the world to get this staff to do something like that. >> we've got to try. >> like most things on this show, it ain't in the budget. so do some research, get back to me. coming up next, spicing up your holiday spread with some gourmet food and drink. but first, costly hospital mistakes. the errors in the operating room and how surgeons are preventing them. you're watching "world news now."