Our favorite Mariachi band was hired to burst into the room and interrupt a speech during a panel discussion at a large scale video gaming conference (PAX) at the Boston Convention and Expo Center last week.   This well served prank was administers by the good folks over at Harmonix (Harmonix is a local Cambridge based company and creator of popular video games Rock-Band, Guitar Hero and Dance Central ).  Also include in the nights entertainment menu was a marching dixieland band and bagpiper !