I’m not a big fan of making people an “audience” without their consent, but this has a nice, light-hearted spirit to it. Kinda brilliant:
The group doing this is called Improv Everywhere, and you may have already seen this rather amazing stunt they pulled off:
For the record, though — I can’t condone or recommend Improv Riffing. But if you choose to indulge yourself at the local mall seventeen-plex, do wear a full body armor. I still wince remembering the beating I took when doing a spontaneous public riff of Schindler’s List.