There is no doubt about it. Fox’s 'Grease: Live' was a knockout success. Even NBC liked the production. Using multiple studios stretching acres of lot and a live audience, Fox managed to take the live musical trend in a whole direction. Now, NBC’s Rob Greenblatt is opening up about Fox’s impressive production, including why they didn’t chose to not use a live audience for their past productions ('Wiz,' 'Peter Pan,' 'Sound of Music') and how that all might change with till fall’s 'Hairspray.'