Meredith Baxter and Crispin Glover being cast in the movies (she was Eve in Ben; he was Willard in the 2003 version) applies, considering that both have not only worked with Michael J. Fox, but did so in Fox's most iconic and well-known projects: Family Ties and Back to the Future.
Moral Event Horizon: Ratman approaches the final line several times before he finally crosses it with murder.
To the rats, he crosses it when he systematically traps and drowns all the females and pups that'd stayed behind when he took the rest to his workplace to kill Jones.
The Woobie: Ratman but more so in the movies than in the book. Crispin Glover's take in particular. His fall into madness is really something to see, and his woobieness is just something that he alone could pull off.