The batusi is the thing where he makes the Vs with his fingers. I need to research this further, but it's definitely in Pulp Fiction, and apparently was a brief craze when the show first went out. Especially in the kind of clubs where vigilantes in tights and masks respond to women trying to pick them up with the line: "You interest me. Strangely. I accept your invitation."
I like the fact that everyone just gets on with dancing even though Batman is there. I guess if Gothamites are used to the city being taken over by crazily dressed maniacs every week, they aren't going to bat an eyelid at Batman propping up the bar. Time enough to get excited