Crouch and stare wide-eyed and straight-faced at someone eating over the rim of their table. Don't respond to anything they say or do
With a group of friends make a game out of seeing how many nachos/tidbits you can ninja off of people's plates without them noticing
drink soda directly from the soda fountain
make a baggie of gross fake barf and then when it's convenient make a dramatic wretching noise and spew the "barf" all over- you get bonus points if other people barf
play a game of butt-table tag with one of the round tables- where you sit on the edge and scoot around on your butts after eachother.
find a booth and constantly switch in and out
find a booth and pile as many people into it as you can
cram as many people into the bathroom as you can (they should be the same gender) all scream at once
find a styrofoam take-out container, punch a hole in it big enough for your finger, stick your finger in it, place a convincing amount of raw hamburger and fake blood around your finger, walk in to the store panting and ask if they have a band-aiid- then show them the finger ^^ (my stepdad did this to me, I almost had a heart attack) make sure you wash your hands afterwards
grab some taco-meat, and some blood-looking stuff, have a friend lay spread-eagled in the center of the store, dump the taco-meat on their tummy, and engourge yourself with your bare hands, everytime someone walks in look up guiltily from your "kill" making sure your face and hands are super messy. Hopefully you'll have a surprised customer walk in, see you , and scream "oh my gawd wtf are you doing?" before you get kicked out or arrested XD
