Food Court Musical

If you haven't heard if Improv Everywhere yet, this is a great example of what they do.  They are self-described as, "[causing] scenes of chaos and joy in public places. Created in August of 2001 by Charlie Todd, Improv Everywhere has executed over 80 missions involving thousands of undercover agents."

Here is another [non food-related] example.

Buy their book, Causing a Scene: Extraordinary Pranks in Ordinary Places with Improv Everywhere for as little as $9.99 via Amazon.