Actually, we did dress up as Star Wars characters(as we, I mean chess club), and just stormed into the cafe at lunch, and started jumping around, swinging light sabers(this one was mine
Amazon.com: Star Wars Episode 3 Electronic Lightsaber Mace Windu Lightsaber: Toys & Games), making zwoo noises, and acting like we had the force(like throwing a hand to throw people). Our female attentive also took the initiative to rig up a lightning mechanism, which shot silly string like material. Was quite classical, everyone lost it, except the principal who suspended chess club for 30 days. =\
We also did this at Long John Silvers and Burger King, but in a more toned version, so as we could fight for 2 minutes, and flee while they started to call the cops. People loved it.