This prank is elaborate but fun: Remove all the drawers from the victim’s desk. Flip the entire desk upside down, replace the drawers, then flip the desk back. Now when the victim open the drawers, all the stuff will fall out straight to the floor.
Photoshop his face into a bunch of funny scenarios and put them up all over the office.
First, determine what your victim’s least favorite thing is—sports team, political view, movie, music, etc. Then cover his or her work area with posters and items celebrating that thing. (For example, if he’s a Chargers fan, cover his office with Raiders gear.)
Borrow all the pictures from his desk and office. Scan the photos, and use a photo-editing program to put monkey faces onto everyone’s faces. Print them out and place them back on the victim’s desk.
Take a small piece of wire and wrap it around the handset cord of the victim’s phone. Place it so both ends of the cord are attached together. Then wait until the victim receives a phone call and watch while they lift the handset and they pick up the entire phone along with it.