Rick,
Sorry to disappoint you, but this isn't an easter egg. There's a very simple (and therefore dull) explanation for it
Microsoft's .chm files are actually nothing more than compiled HTML files (HTML being the language of web pages). In fact the chm suffix for these files is just short for
Compiled
HT
ML.
So the Help system (not just for calc, for pretty much most Microsoft applications) is little more than a user interface built around the Internet Explorer system components. The help files work like web pages, and the item on the menu that you saw simply allows you to load up any web page.
You want to see something else? Grab any of these help windows (the one from calc will do just fine), and open a browser window, pointing at your favourite web site. Using your mouse, grab the icon from the left end of the browser's address bar, and drag it onto the right-hand panel of the help window. Wait a moment whilst the page loads and... the web page displays in the help application.
Hope this is interesting to someone
Ta ra
Alan