I love everything about this; venue, audience, impromptu-ness of the performance, outfit, song, singer, that it happened on Halloween. The only thing that could possibly make it better would be to see audience members dancing and otherwise enjoying themselves even more. When I listen to music I really enjoy or can immerse myself in, I can't help but stand up or move a lot. I know of a handful of other musicians with this characteristic and I see many instructors attempting to stamp out it of their students because they see it as a performance distraction, but I never paid that much mind to my private instructors. Whole body movement was a dead giveaway visual clue if I was actually playing music in my university ensembles or just playing notes.