"We need not to be let alone. We need to be really bothered once in a while. How long is it since you were really bothered? About something important, about something real?"
Tell the man at the deli counter that the slices are still too thick until he ends up shredding the meat. Then tell him it's too thin. Just to irritate him.
Have a trolley race (no, I'm not that immature but it's an idea).
Re-arrange the tins of baked beans. (I assume Walmart has those- right?)
Make a fish puppet and hide behind the fish/meat counter. Whenever somebody passes by or looks at the fish or meat, raise the puppet and say in a croaky voice "Don't eat me..."
Place some cat food in the pate isle; see who falls for it.
It is only a novel... or, in short, only some work in which the greatest powers of the mind are displayed, in which the most thorough knowledge of human nature, the happiest delineation of its varieties, the liveliest effusions of wit and humour, are conveyed to the world in the best-chosen language — Jane Austen, Northanger Abbey