The Aristocats is Disney's 20th animated feature film, and the first one entirely produced after Walt Disney's death in 1966. Since the 50's, Walt had started working on other projects like amusement parks and tv programs, so the animation team was used to his absence (which grew bigger with each year), and had learned to think like Walt, so when he was gone, they could still work on a new feature that Walt would be proud of.
But Walt wasn't completely unaware of what the studio's next feature would be. He actually gave the thumbs up to the team to start work on the Aristocats story.
The film was originally intended as a 2-part live-action film for Disney's weekly tv programme, but Walt decided it would be better as an animated feature.
The film was produced the same way as its 3 predecessors from the same decade (101 Dalmatians, Sword in the Stone and Jungle Book) using the Xerox machine to create each frame faster and cheaper. But by no means does it look the same as these previous films.
Even though the Xerox process gave a certain aspect to the animation, each film has its particular aesthetics. In the case of the Aristocats, artists and animators found a way to combine the contemporary style of the Xerox process with a more painterly style evoking the turn of the century Paris.
The backgrounds (900 of them) painted for the film are absolutely beautiful. Much more detailed than the previous 60s movies, perfectly representing the artists from that era. You can tell that this style greatly influenced the films of Sylvain Chomet (Triplets of Belleville and The Illusionist).
With a great cast of musicians like Phil Harris as the voice of Thomas O'Malley, and the Scatman Crothers as Scat Cat, the film is filled with great performances and awesome songs.