Hey, It's That Sound!: The zoo hyena's laugh done by Dallas McKennon would later become a rather popular stock sound effect, with the "voice" of Ripper Roo from theCrash Bandicoot series being the most well known usage.
Keep Circulating the Tapes: The version that Disney animated in the 1.37:1 Academy ratio, for theaters unable to show widescreen movies, has only received one official home video release, when it was released on VHS and LaserDisc. Reissues of the movie on newer formats only feature the CinemaScope version, leaving the Academy version unable to view, aside from some clips included in some of the bonus features.
Screwed by the Lawyers: Peggy Lee sued Disney when the film was released on VHS and LaserDisc, citing that her contract did not allow them to use her voice on video. She eventually collected a seven figure sum, and Disney began including in their contracts rights to "media not yet existing." The same thing happened with the Mexican Spanish dub, as Tramp's voice actor (Roberto Espriu) sued Disney for the same reason, forcing Disney to do another dub with a different cast.
Talking to Himself: Peggy Lee, Dallas McKennon, Lee Millar and Bill Thompson each perform more than one role in the film.
This was the first animated feature screened in Cinemascope, the first Disney animated feature to be distributed under Buena Vista Distribution (as opposed to RKO Radio Pictures, as previous ones had) and also one of the first animated Disney films to be (mostly) based on an original story by Joe Grant.
The casting of Peggy Lee as voice actor and songwriter was also one of the earliest examples of a "big name" in an animated feature at the time.
Trusty was supposed to die after the dogcatcher's wagon hit him, but Walt Disney didn't want another serious death, following the trauma Bambi's mom's demise caused many children.
Boris the Russian Wolfhound (who appears at the pound) was originally supposed to be the male lead of the film, having Tramp's role. However, the title "Lady and Boris"..."just didn't have the right ring to it".
Tramp/Boris was also supposed to have had a song, called "I'm Free as the Breeze", which he sang about his life as a happy stray. It was cut when the film was retooled.
In one early version, the rat spoke and was more of a troublemaker than a genuine menace. He would have had a Jersey gangster sort of personality. His name would also have been Herman.