Based on the children's book series Basil of Baker Street by Eve Titus, it draws heavily on the tradition of Sherlock Holmes with a heroic mouse who consciously emulates the detective; Titus named the main character after actor Basil Rathbone, who is best remembered for playing Holmes in film (and whose voice, sampled from the Red-Headed League was the voice of Holmes in this film, 19 years after his death). Interestingly, Sherlock Holmes also mentions "Basil" as one of his aliases in the Arthur Conan Doyle story "The Adventure of Black Peter".
After the failure of the previous Disney animated feature film, The Black Cauldron, this simpler film proved to be a success upon its initial release in 1986. As such, the new senior management of the company were convinced that their animation department was still a viable enterprise and this set the stage for the Disney Renaissance. It should be also noted that this is the film which saved Disney's Animation Studios from going bankrupt at the time.
In London 1897, a young Scottish-Welsh mouse named Olivia Flaversham was celebrating her eighth birthday with her toymaker father, Hiram. Suddenly, Fidget, a bat with a crippled wing and a peg leg, bursts into the Flavershams' workshop, and after a short struggle disappears with Hiram.
It was later revealed that the evil Professor Ratigan kidnapped Hiram to create a clockwork robot which mimics the Queen of the Mice so Ratigan can rule England. Hiram refuses to take part in Ratigan's scheme, whereupon Ratigan orders Fidget to capture Olivia. If Hiram refuses to cooperate, Ratigan will have Olivia fed to his pet cat, Felicia.
Then Olivia searches to find Basil of Baker Street, a world-famous detective and Ratigan's archnemesis. Dr. David Q. Dawson stumbles upon Olivia, and helps her find Basil's residence. At first Basil was reluctant, but when Olivia mentions the peg-legged bat that kidnapped her father, Basil realizes that this was his chance to capture Ratigan. Basil and Dawson then uses Sherlock Holmes' pet, a Basset Hound named Toby, to track Fidget's scent to a nearby toy store. Fidget was surprised by Basil, Dawson, and Olivia in the toyshop where he was stealing clockwork mechanisms and toy soldiers' uniforms for Ratigan's plan. He hides and later traps Olivia by ambushing her from inside a toy cradle. Basil and Dawson pursue Fidget but become entangled in some toys and fall behind, giving Fidget enough time to escape with all the materials he needs, along with Olivia.
While searching the shop, Dawson discovers Fidget's forgotten checklist, which details everything Fidget has taken with him. Basil and Dawson return to Baker Street, where Basil discovers by means of close examination and some chemical tests that the list came from the riverfront, and they look for a small tavern near the Thames where the sewer would connect to the river. Basil and Dawson disguise themselves as sailors and go into the tavern, inquiring for Ratigan. As they wait, Fidget stumbles through the pub. The two follow Fidget through some pipes to Ratigan's headquarters, only to discover that Ratigan and his henchmen had prepared for their arrival. Triumphant, Ratigan ties them to a spring-loaded mousetrap, connected with a Rube Goldberg machine made of a gun, a crossbow, an axe, and an avil. Ratigan sets out for Buckingham Palace, where Fidget and his accomplices manage to defeat Royal Guard and kidnap the queen. Basil briefly despairs at being outwitted, but snaps out of it just in time to deduce the trap's weakness and escape.
Back at Buckingham Palace, Ratigan forces Hiram to operate the toy Queen, while his men pose as Royal Guards and the real Queen was being taken by Fidget to be fed to Felicia. The fake queen declares Ratigan ruler of all Mousedom, and, after thanking his robotic consort he announces his tyrannical plans for his new "subjects", including several unfair taxes. Just then, Basil, Dawson, and Olivia saves Hiram and the real Queen, and apprehend Fidget along with Ratigan's other two henchmen (Bill Lizard and one mouse). Basil then seizes control of the mechanical mouse-queen, forcing it to denounce Ratigan as an impostor and tyrant, all the while breaking into pieces. The crowd, enraged by Ratigan's treason, start climbing onto him and defeating his shanty guards. Ratigan frees himself and escapes on his dirigible with Fidget, and holding Olivia hostage.
Basil, Dawson, and Hiram create their own craft with a matchbox and some small helium-filled balloons, held under the Union Jack. A high-speed chase above the city ensues. Ratigan throws Fidget (who can't fly) into the Thames River below to "lighten the load", and then attempts to drive the dirigible himself. Basil jumps on to the dirigible to confront his nemesis; however, with no helmsman, Ratigan was unable to steer his craft, and it ends up crashing straight into Big Ben. Inside the clock, Ratigan and Basil face off in a final battle. Basil rescues Olivia and safely delivers her to Hiram, who was still on the balloon with Dawson. Ratigan plunges into Basil, and they both fall onto the clock's hour hand. The fight ensues, and Ratigan begins to viciously thrash Basil. It seems as if Basil's luck was about to run out until the clock bell tolls and Ratigan plunges off the hand taking Basil with him, however Basil saves himself just in time with the motor of Ratigan's destroyed dirigible.
Back at Baker Street, Basil and Dawson recount their adventures as well as the queen's gratitude to their saving her life, and afterwards, the Flavershams leave. Dawson figures it's time for him to leave as well, but the scene was interrupted by a distraught new client. Basil then persuades Dawson to remain as "my trusty associate, Doctor Dawson, with whom I do all my cases".
The layouts were done on computers, and the use of video cameras made a digital version of pencil testing possible. The movie was also notable for its early use of computer generated imagery (CGI) for a chase scene that takes place in the interior of Big Ben. The movements of the clock's gears were produced as wire-frame graphics on a computer, printed out and traced onto animation cels where colors and the characters were added. The Great Mouse Detective is sometimes cited as the first animated film from Walt Disney Pictures to use CGI; in reality, 1985's The Black Cauldron has this distinction.
Olivia was originally intended to be an older character with the potential as a love interest for Basil or even an infatuated Dr. Dawson, before it was decided that she should be a child to better gain audience sympathy. While Basil and Dawson were visually based on Rathbone and Bruce, their voices and personalities were not. Basil's voice was based on Leslie Howard’s portrayal of Henry Higgins in the film Pygmalion while Dawson's voice was based on Disney animation legend Eric Larson. "We didn’t want to make them simply miniature versions of Basil Rathbone and Nigel Bruce," Clements affirmed. "Dawson’s not a buffoon. He’s a foil for Basil but also a warm and caring person."
Disney's decision to name the film The Great Mouse Detective and not Basil of Baker Street was unpopular with the filmmakers. Animator Ed Gombert wrote a satirical interoffice memo, allegedly by studio executive Peter Schneider, which gave the preceding films the following generic titles:
- Barrie Ingham as Basil of Baker Street, a detective, based on the fictional sleuth Sherlock Holmes and the primary protagonist of the film. His main goal is to get Professor Ratigan behind bars and rescue Olivia Flaversham's father while simultaneously preventing a royal assassination. There are a few differences between Basil in the book series and in the film version, such as mercurial moods in the latter. He also plays the violin rather well in the movie, whereas the book series stated Basil's violin playing was atrocious—instead, Basil played the flute.
- Vincent Price as Ratigan, Basil's archenemy and the primary antagonist of the film. Based on Professor James Moriarty from the Sherlock Holmes stories, he plots to seize control of the British monarchy. He and Basil are long-established archenemies. In the book series, it is revealed his given name is Padraic and that Ratigan is, in fact, a mouse. At the end of the film, he is knocked off Big Ben and disappears into the deep chasm below, following a fierce battle with Basil, similar to the Sherlock Homes story "The Final Problem".
- Val Bettin as David Q. Dawson, previously of the Queen's 66th Regiment in Afghanistan. His character is based upon Dr. John H. Watson from the Sherlock Holmes stories. The interaction between him and Basil mimics that of Watson and Holmes, as Dawson is constantly amazed by Basil's deductions. He eventually becomes Basil's associate, friend, and personal biographer. In the film, the animators modeled the character after Nigel Bruce in both appearance and character.
- Susanne Pollatschek as Olivia Flaversham, a young female mouse of Scottish descent who seeks Basil's help in finding her toymaker father.
- Candy Candido as Fidget, Ratigan's bumbling, but sly and creepy bat henchman. He tends to do the dirty work for his boss. He has a crippled wing and a peg leg, and as a result he cannot fly properly. Ratigan throws him off the side of his flying machine near the end of the film, and he falls into the Thames.
- Frank Welker as Toby, Basil's trustful Basset Hound. He technically belongs to Sherlock Holmes, who lives above Basil.
- Alan Young as Hiram Flaversham, Olivia's loving Scottish father. He works as a toymaker and is kidnapped by Fidget to make the Queen Mousetoria robot for the evil Ratigan.
- Frank Welker as Felicia, Ratigan's massive and pompous pet cat. Ratigan calls upon her by ringing a special bell to dispose of traitors or anyone who makes him angry. She is attacked by Royal Guard Dogs in the final part of the film and not seen again.
- Diana Chesney as Mrs. Judson, Basil's housekeeper. She adores Basil, but gets very annoyed when he mistreats her good pillows by shooting them with a pistol. Based on Mrs. Hudson.
- Eve Brenner as Queen Mousetoria, whom Ratigan attempts to depose. She is a parody of Queen Victoria and the setting for this film coincides with the real Victoria's Diamond Jubilee (as can be seen with humans entering Buckingham Palace at the same time the mice are).
- Barrie Ingham as Bartholomew, one of Ratigan's henchmen. He meets his end early on during Ratigan's song when he drunkenly calls his boss a rat; enraged, Ratigan throws him outside and summons Felicia, who devours him.
- Basil Rathbone as Sherlock Holmes, the famous human detective who lives above Basil. His voice is taken from clips of the original Sherlock Holmes films.
- Laurie Main as Dr. Watson, the medical associate/partner of Sherlock Holmes, who also lives above Basil. Unlike Rathbone, voice clips of Nigel Bruce were not used for the cameo part of Watson.
- Wayne Allwine, Tony Anselmo, Walker Edmiston and Val Bettin as the Thugs
- Charles Fleischer - Addtional voices (uncredited)
The film was well received by critics during its initial release, including a "two thumbs up" rating from American film critics Gene Siskel and Roger Ebert. The film also maintains an 81% "Fresh" rating on Rotten Tomatoes, based on 16 reviews. London's Time Out magazine wrote, "As usual with film noir [...] it is the villain who steals the heart and one is rooting for in the breathtaking showdown high up in the cogs and ratchets of Big Ben."
This film did fairly well at the domestic box office, garnering around $38,625,550 over a budget of $14 million during its initial release. Its moderate success after its predecessor's failure gave the new management of Disney confidence in the viability of their animation department. It should be noted that its performance at the foreign box office isn't documented.
Despite its financial success at the domestic box office, The Great Mouse Detective was not released on home video until after its theatrical re-release in 1992; this first home video release of The Great Mouse Detective eventually became part of the Walt Disney Classics series. In August 1999, it was reissued on VHS with a game sheet inside it as part of a contest. It was later released for the first time ever on DVD in 2002, with a short making-of feature on how the film was made.
A new "Mystery in the Mist Edition" of The Great Mouse Detective was released on DVD on April 13, 2010 and on Blu-ray Disc on October 9, 2012. Unlike previous home video releases, which all used the 1992 reissue title print (The Adventures of the Great Mouse Detective), this DVD restored the original 1986 title card, which had previously not been seen since the original 1986 release. The DVD also has the film in 1.78:1 aspect ratio Widescreen revealing more picture, bringing it closer to its original theatrical aspect ratio. This edition has not been released in Europe.
- "The World's Greatest Criminal Mind ", Music by Henry Mancini, Lyrics by Larry Grossman and Ellen Fitzhugh, Performed by Vincent Price.
- "Let Me be Good to You" Music and Lyrics by Melissa Manchester, Performed by Melissa Manchester.
- "Goodbye, So Soon" Music by Henry Mancini, Lyrics by Larry Grossman and Ellen Fitzhugh, Performed by Vincent Price.
- This film is sometimes considered, by fans and animation historians, to be the unofficial start of Disney's second golden age, also known as the Disney Renaissance. This is mostly due to the fact that this movie had saved Disney Animation Studios from going completely bankrupt at the time.
- This was the last animated Disney film to heavily use the classic Jim McDonald Disney cartoon sound effects. Though some later Disney films did use the sound effects for humorous moments (like most notably Aladdin).
- While the film's script took roughly to 4 years to develop, the animation took only 1 year to finish, thanks to use of computers at the time..
- This film is the first in the Disney animated canon to feature the voice talents of Frank Welker.
- Despite the fact that this film, and the book its based off of, are considered parodies of Arthur Conan Doyle's novels involving the character Sherlock Holmes, this film is deeply beloved by the Sherlock Holmes fanbase with its various similarites.