If you want to be mean (and colorful) fill the cups with colored water or Kool-aid (or dye if you're really bad). You could also fill the cups with s...
Step 4: Tricks
Get creative! Floors aren't the only surfaces that can be covered, anything that's relatively flat will do. Cup someone's desk, car, kitchen table/counters, or closet floor. Remember, the goal is extreme inconvenience!
Make designs or elaborate figures. Add a prize to the mess (say in the middle of 6 feet of cups) to offset the prank if you want to be nice.