Foudn this and I thought it was fun and helpful. Feel free to use this on your charries if you want ^_^

If you don't know what a Mary-Sue is, check out the Wikipedia article here

The Mary-Sue Litmus Test!

Or if that doesn't work:
http://www.springhole.net/quizzes/marysue.htm

And if you are still having issues, just go to Google, type "Mary-Sue Litmus test" and click on the first link that pops up ^_^