To those of you who wish to mention fictional characters in your book.
CORNERS, the book I'm writing right now, has given me a lot of grief due to my own stupidity. It's about 4 kids visiting 25 books, of which 9 ended up being not in public domain. I suppose I was thinking with my behind rather than my head when coming up with the idea. Since then I've been researching the issue and have switched to making it a parody that will be revealed later in the book by mentioning the actual book titles and character names. As long as I don't have them talk, I can possibly get away with it. Still thinking about how to frame it.
Meanwhile...today I stumbled on this fantastic blog post by an attorney shedding light on the subject. Read it. It has a wealth of information on how you can use characters' names, why, in what context, and how far you can go. It also has a wealth of links to other articles on the subject. Once finished with my book, I plan to write a blog post about what I did and how I did it. For example, I will be making fun of the whole "writer has to be dead for 70 years" thing required for the book to be in public domain, etc.
This is precisely the reason why all my books are free and are licensed under Creative Commons license. Because, naturally, one day I will be very famous and everyone will want to use my characters in their books. I CAN'T BLOODY WAIT.