Acting for Two: Barrie Ingham voices both Basil and the unlucky Bartholomew. Interestingly, that makes two out of the three characters in the movie who call Ratigan a rat (the other being Olivia), and one out of two that live to tell the tale.
Actor Allusion: When Bill the Lizard tries to assure Ratigan that he's a "big mouse" to convince him to spare Bartholomew, his voice suddenly switches to a high-pitched falsetto, referring to the particular big mouse his voice actor was best known for providing.
Awesome, Dear Boy: Price on his role as Ratigan. He had stated that Ratigan was his favorite film role.
Having two songs written for him certainly helped.
Dueling Movies: With An American Tail, another animated movie about mice coming out the same year (though it didn't come out until a few months afterward). While the film made its money back, American Tail was a smash hit and, at the time, the highest-grossing animated feature ever made. Both of these things would factor into Disney deciding to re-beef their animation department.
Executive Meddling: Largely averted, as Jeffrey Katzenberg had little to no faith this movie would be any good. Most of his attention was spent on meddling with The Black Cauldron, which would become a failure. Katzenberg did, however, demand the title of this film be changed from "Basil of Baker Street" to simply "The Great Mouse Detective", a move that inspired an infamous fake memo that became a category on Jeopardy!. Two of the four directors have since said they've always hated the new title. However, those directors may have had some solace in the title being changed to "Basil the Great Mouse Detective" in some international versions, including Australia.
I Am Not Shazam: The lead dancer at the bar is listed in the credits as "Miss Kitty Mouse," but, Fanon aside, this doesn't actually appear to be her name. Rather, it's a description of her. She isn't "Miss Kitty Mouse," but "the Miss Kitty mouse."
Originally, Ratigan was a very ugly mouse mistaken for a rat, instead of a rat willingly passing for an ugly mouse.
The Walt Disney ClassicsVHS cover provides the Image Source for this film on TV Tropes. That tape has the 1991 green F.B.I. warning screens, a brief trailer for Musker and Clement's next film, Aladdin, the lilac-blue cursive Feature Presentation bumper, a second variant of the early 1992 Sorcerer Mickey Walt Disney Classics black diamond logo (the logo's jingle fades out abruptly; 101 Dalmatians had it fade out gradually. The next Classics tape would distort the jingle for the rest of the line), the 1990 Walt Disney Pictures logo, and the film, which used the The Adventures of The Great Mouse Detective title. The film is followed by a silent 1990 Walt Disney Pictures logo and home video trailers for the next two Classics releases: The Rescuers, and Beauty and the Beast, before the tape ends. The LaserDisc has either the 1989 Walt Disney Classics logo or the 1986 Sorcerer Mickey Walt Disney Home Video logo prior to the WDP logo and the film.
This film was intended to be reissued in the Walt Disney Masterpiece Collection line as well in 1999, with trailers on tapes such as The Adventures of Ichabod and Mr. Toad billing it as Disney's Masterpiece. TAOIAMT ended up being the final new release and one of the last releases in the Masterpiece Collection period, though; it was discontinued and this tape had no branding. It only has the Gold Walt Disney Home Video logo, trailers, and the zoom-out sapphire blue Feature Presentation bumper before the Walt Disney Pictures logo. This release retained the The Adventures of The Great Mouse Detective title; the original title would not be restored until the "Mystery in the Mist" edition on DVD and Blu-ray in The New 10's.