Some of these food places are always going out of business or having grand openings. There are dozens of them spread over 3 major areas downtown, but I guess any large mall would work for this prank in the suburbs. We created a restaurant name and used PowerPoint and PhotoShop to create grand opening flyers that promised free entrees and sandwiches and all other kinds of stuff. Then we each took about 40 or 50 of these and went down to the entrances of the food courts and handed all of the flyers out. It was hilarious and really didn't hurt anyone other than wasting their lunch hour.
Few things are as amusing as mass confusion.
But one of those things is being responsible for the confusion. I'm A Rocketman Get some small model rocket engines and igniters, some wire, and a nine-volt battery. Hook up the engines to the igniters and the wire, and then connect one side of the battery. I saved this one for last because it's the most advanced of the whole bunch. And, as funny as the mental image is, it should be attempted by only the most accomplished prankster, if any at all.