Toshio's spirit is often heard meowing throughout the film. Not only does this imply that his spirit merged with his deceased cat Mar, but it also relates to an old Japanese legend where the damned spirits of lost children become strays and as a result, produce a cat's meow.
The house used in this film was not a constructed set but a real location, which had to be rented for film production. It became a tourist attraction following the franchise's popularity. The house was demolished in 2019.
The only film in the entire series that has the ghostly version of Kayako speak, and she simply says "Kobayashi-kun" before giving Kobayashi a kiss of death.
During the initial shooting, Takako Fuji was only emoting anger and rage. Takashi Shimizu directed her to emote other feelings in subsequent takes, so as to show that Kayako was once human and that she might even be sad and misunderstood.