this is possible in many ways, using JavaScript. However the easiest way, although not the most configurable is to add a link pointing to the page itself and use the title attribute of the anchor, something like this:

<a href="#" title="Papaya - a type of fruit, widely used in Thailand to make wonderful dishes, such as Som Tum Thai.">papaya</a>

Go on my blog about [URL="http://dracula-transylvania.blogspot.com"]Vlad the Impaler[/URL] and look for the second item in the list of latest posts, the one with the text "Vlad Dracula conquers Wallachia's Throne.". Hold the mouse over it to see how it looks. In this case it is a real link, pointing to another page, however putting the href="#" will make it do...nothing...it'll point the the current page.

If you don't like it, there is some javascript to put in the page, for this you have to know just a little bit of JS programming.

Hope this helps,
radu