Remove the shower head and place a chicken bouillon cube in it, then put the head back on.
 640
1  

Hide all of the desktop icons on someone's computer and replace the monitor's wallpaper with a screen-shot of their desktop.
 804
0  

Hide an alarm clock in someone's bedroom and set it for 3:00 a.m.
 743
0  

Fill someone's hair-dryer with baby powder.
 690
1  

Put a "Please Use Other Door" sign on the entrance to your office building if it only has one entrance.
 1372
1