*Note:I do not take credit for these ideas, I found them on the internet and had to share here*
1-wander through the store dressed in all black with a fake walkie-talkie humming the Mission Impossible theme. When someone asks what you're doing, scream "LOOK OUT!!!" and push them behind a shelf
2-Pass out bananas to random people and snicker loudly after they take one.
3-Buy 350 packets of tuna and scream "THIS CAN'T BE RIGHT!!! YOU HAVE TO PUT SOME BACK!!!" once the cashier tells you the price
4-Walk around looking confused in the CD section and ask someone where you can find some "musical devices"
5-when the announcer-thing comes on, throw yourself on the floor and scream "THE VOICES!!!THEY'RE BACK!!!"
6-start a fish stick fight
7-walk up to random people and give them giant bear hugs. Then scream "I MISSED YA, MAN!!!!!!!"
8-(this requires a friend) Jump in a cart and have a friend push you around screaming "The British are coming!!!"
9-walk up to an employee and murmur "code red in aisle 3" and see what they do
10-slip a bunch of female objects (Tampons, thongs, bras, etc.) in a macho-looking man's cart.(just make sure he doesn't have any girls with him)
11-attempt to fly off a high shelf
12-throw confetti on random people walking into the store
13-whisper "I know your "little secret"' to people in the checkout line
14-stand inside the freezer at the frozen food section
15-walk up to employees and whisper "I saw dead people...They want me to take you away...to aisle 8..."