I think my best was at a bar. I went around and got everyone to agree to walk out of the bar as soon as the band started. The band was a local and most of us knew them so about 50 people got up and walked out. The band and bartender had no idea what was going on. The only problem was once we were outside, then what! We just stood around about 5 Min.s BSing and walked back in and said, April Fools! It was a good one on them. (Only 2 people in the bar that didn't do it!)
Peace. And may you still pull a good gag or two today! Rustic