Well, not exactly, "fan" fiction, but of the same ilk. After the success of Charles Dickens' Posthumous Papers of the Pickwick Club in 1837, George Reynolds took the characters on a new picaresque journey in Pickwick Abroad: or, the Tour in France published in monthly parts from 1837-38. Our first single-volume edition from 1839 acknowledges its debt to Mr. Dickens (or "Boz"), but also cites a review from The Age boasting that "'Pickwick Abroad' is so well done by G. W. M. Reynolds, that we must warn Boz to look to his laurels." Reynolds was surely throwing down the gauntlet, but by using Dickens' own creations.
How could this happen? At that time, an author did not have any real rights over the characters he or she created. The original work could get copyright, but the story and the characters were up for grabs. This led to works like Pickwick Abroad as well as other adaptations of popular novels. The law was not changed until Frances Hodgson Burnett fought for full control of her characters later in the century. Pickwick Abroad was a tremendous success that earned Reynolds 800 pounds.
To see the original, ask for Val 826 D55 U6. Pickwick Abroad is Sine C76pic.