Quiz

There have been reports that the enormous rat Ben was not portrayed in the film by an actual rat, which is not true. Ben was portrayed by a Gambian pouched rat (Cricetomys gambianus), a distant relative of the brown rat (Rattus norvegicus), the species used in the film. Gambian pouched rats, while fairly docile, can grow to a body length of as much as 10-17 inches from the head to the base of the tail, with the tail about the same length or longer, and can generally weigh anywhere from two to over six pounds.

Over 500 rats were used in the film and subjected to extensive training before being put on the set. The rats were set into categories for the actions that they would perform.

The film prominently features the song "Ben" by Michael Jackson; this song was written specifically for the film L'ultima carica di Ben (1972), which was the sequel to the original version of Willard e i topi (1971).

The filmmakers suggested making Willard look like a very rat-like human and requested that the film's the make-up artists make Crispin Glover look as unattractive and nervous-looking as possible by accenting the hard angles of his face, making him pale-skinned and dark around the eyes, and making his distinct nose stand out.

Joaquin Phoenix and Macaulay Culkin both turned down the role of Willard Stiles for this film.