The English dub version of the movie is the only movie where Rodan is referred to by his real name, Radon.
Despite the film's English title, "Godzilla vs. Mechagodzilla II," the film is not a sequel to Godzilla vs. Mechagodzilla (1974). A later film featuring Mechagodzilla was released in western markets as Godzilla Against Mechagodzilla (2002). In their original Japanese language, all of these films are differentiated by what word is used for "versus". The original 1974 film uses "tai", this film uses "VS", and the 2002 film uses "X".
Originally intended to be a remake of King Kong vs. Godzilla (1962). The producers, however, considered Turner Entertainment's asking price for the rights to King Kong too high. They then planned on using Mechani-Kong from King Kong Escapes (1967), but they feared this would violate Turner's copyright. Toho ultimately decided to use Mechagodzilla, although the Mechani-Kong theme was used in the film.
Proportional to the film's run-time, this film has the most Godzilla screen-time out of all the films in the franchise (around 20% of the film).
An incorrect rumor among fans is that Lt. Berger, the white woman co-piloting Mechagodzilla, was meant to be revealed as an android, a human-like robot at the end of the film. However, this is a misconception arising from a mistranslation of a deleted scene where Berger is jokingly referred to as a "replicant", comparing her stern attitude with the artificial humans from Blade Runner (1982). The character was never actually considered or meant to be an android.