How to amuse yourself in a department store...

Take shopping carts for the express purpose of filling them and stranding them at strategic locations.
Get boxes of condoms and randomly put them in people's carts when they don't realize it.
Set all the alarm clocks to go off at ten-minute intervals throughout the day.
If the store has a food court, buy a soft drink, explain that you don't get out much and ask if they can put a little umbrella in it.
Try on bras over top of your clothes.
Make a trail of orange juice on the ground, leading to the restrooms.
While walking around the store, sing in your loudest voice possible "I smell sex and candy."
Walk up to an employee and tell him in an official tone, "I think we've got a Code 3 in house-wares," and see what happens.
Tune all the radios to a polka station; then turn them all off and turn the volumes to "10."
Challenge other customers to duels with tubes of gift-wrap.
Re-dress the mannequins as you see fit.
Test the fishing rods and see what you can "catch" from the other aisles.
Put M&M's on layaway.
Move "Caution: Wet Floor" signs to carpeted areas.
Set up a tent in the camping department; tell others you'll only invite them in if they bring pillows from Bed and Bath.
Contaminate the entire auto department by sampling all the spray air fresheners.
Nonchalantly "test" the brushes and combs in Cosmetics.
When someone asks if you need help, begin to cry and ask, "Why won't you people just leave me alone?"
Look right into the security camera, and use it as a mirror while you pick your nose.