The english version of the aforementioned NIMH: The Unauthorized Sequel now exists at http://www.karthurville.com/robin/ufstories/ntus/ntusindex.html. It was originally written and drawn by Ken Singshow and was translated by uberfan Kristin Blomstedt. Unfortunately, it likely won't be completed since the author recieved a nasty letter from lawyers from Warner Brothers (who own the foriegn rights to The Secret of NIMH) and because his severe workload prevented him from spending much more time on it.
Shannon Doherty does the voice-acting for Teresa, the older sister of Timothy, the mouse that was sick, in The Secret of NIMH.