The film is partially autobiographical. When Hayao Miyazaki and his brothers were children, his mother suffered from spinal tuberculosis for nine years, and spent much of her time hospitalized. It is implied, yet never revealed in the film, that Satsuki and Mei's mother also suffers from tuberculosis. He once said the film would have been too painful for him to make if the two protagonists were boys instead of girls.
The names of the two girls, Satsuki and Mei are a play on the word May. "Satsuki" is an old Japanese word for May, and "Mei" is the Japanese pronunciation of the English word "May".
The forest creatures and title characters of this movie got their name when Mei, the little girl who first sees them in the film, mispronounces the word "troll". At one point in the original Japanese language version, when Satsuki first finds Mei sleeping in the grove behind their house, Mei tells her sister she saw a "totoro". Satsuki replies, "Totoro, do you mean troll, from the storybook?" and Mei nods in agreement. This aspect of the story was left out of the 1993 Fox English version, probably because the difference between ""to-ro-ru" (the Japanese pronunciation of "troll") and "to-to-ro" would have been lost on English-speaking audiences. The quote is included in the 2006 Disney English version.
Hayao Miyazaki originally conceived the characters Satsuki and Mei as a single girl. He wanted to add suspense to the latter half of the film, and he felt it wouldn't work with just a single girl, so he split her into two separate girls. The original girl had features of both Satsuki and Mei, and was 7: halfway between the ages of Satsuki (10) and Mei (4).
On its original theatrical release in Japan, it was double-featured with Grave of the Fireflies (1988) as the film was believed to be too big a financial risk as a standalone release.
The movie initially did not do well at the box office, and did not break even until about two years after the release when stuffed dolls based on the King Totoro character hit the shelves.
During the 2005 World Expo in Japan, a classic Japanese house modeled after Satsuki and Mei's house, was built and opened to the public.
Outside of the Japanese Academy Awards, which historically ignored animated films until 1998's Princess Mononoke (1997), "My Neighbor Totoro" won an award from every major Japanese film awards including Best Film from both the Mainichi Film Award and Kinema Junpo, as well as the Blue Ribbon's Special Award.
Some people have speculated that the name Totoro comes from the city Tokorozawa in Japan. Hayao Miyazaki grew up around here and has memories of children mispronouncing Tokorozawa as Totoro.
The film is included on Roger Ebert's "Great Movies" list. He even went on to call it "One of the Most Beloved of All Family Films."
Dakota Fanning was born in 1994, six years after the film's original release, but joined the voice cast for the 2005 re-release (at which point she was 11).