OH, and this is only my 2nd Instructable, so don't be too harsh on the comments please.
Step 1: Supplies
Some Tape (Scotch or Packaging, either works)
A mouse (your victims mouse)
Step 2: Setting Up the Prank
Look at the pics if you need any help.
Step 3: Waiting for the Victim...
Step 4: And...
Have fun! And try not to laugh too much when your victim goes insane!