Heineken asked people to persuade their friends, boyfriends, colleagues, ... to go and watch a classic concert on 21st February 2010. However on that same day there was the most important game of the year for AC Milan as they were playing Real Madrid. Many guys were tricked to go to see the concert but they didn't know what was going to happen next.
In my opinion one of the best viral marketing stunts in beer ever pulled off!