This is a really fun prank that you can play on a co-worker who may not be very educated on the finer points of Microsoft Word.
NOTE: Don't get yourself in trouble... if you do this and get in trouble, do NOT blame me! This one is far better to do to someone with a sense of humor, and with whom you're already engaged in a battle of pranks. Have a heart and bail them out before they get too pissed.
Here is how it is done:
Step 1 – From the Tools menu, select AutoCorrect.
Step 2 – From the AutoCorrect window, you can exact all kinds of mischief.
You could, for instance, decide to replace the word "but" with "turd burglar", and the word "and" with "panties" (see below).
Some Suggestions for changes:
Replace: if With: stiff one
Replace: so With: suck
Replace: have With: horny etc, etc, etc… you get the gist !!
NOTE: Timing for any good prank is critical. A good time to play this prank is when said coworker has a big report due.