Microsoft Word 97 and above has a lovely feature called AutoCorrect. If you type in a word like "teh", it assumes that you really meant "the" and corrects the spelling of the word automatically.
You can view the entire list of words by going to Tools and AutoCorrect. The list is entirely editable and easy to change.
So what's stopping you from making a few changes?
Just head down the list and find a few easy to misspell words and have a little fun. A great one to start with is "the". Type in "the" and reword it to "teh"! But don't stop there. Type in "boobs" and make the correct spelling "knockers". Let your imagination run wild.
Just remember the words you set up so that you can easily change the list back at a future time.
Most people get frustrated and assume that Word is misbehaving. They never suspect it is a coworker that is defective.