Open a can of whipped cream and cover your mouth with it, then roll on the floor making creepy noises, like you have rabies.
Dress like a Wall-Mart employee and run up to different people asking, "Want some cheese?!" then steal their trolley and run away laughing.
Throw tomatoes and spit at the security camera, then paint your face like a fruit and hide in the fruit section, close your eyes, and when people look at the fruit, scream loudly. Then hide in clothes section and stay there overnight.
When the employees announce something, yell "Those voices again! Nooooooooo!" And run around Wal-Mart like crazy, knocking down clothes from their holders xD
-Lie in the middle of a busy floor and if anyone tells you to move say 'I have to because Big Bird told me too and he's my leader!!' Then do a creeper smie at anyone who looks at you