I know Walt Disney hated the Xerox look of the film, but I think that's one of the main reasons why its so charming. For an animator, it's got that sketchy quality that we all admire, like a colored pencil-test. The backgrounds are really unique for a Disney picture, where everything looks flat & has that graphic style. It may have been an eyesore to Walt, but to us animators & cartoonists, it's eye candy.
The middle of the film is my favorite, from the Twilight Bark sequence up the the last scenes at Hell Hall . & my favorite characters in the film are not the dalmatians, but the trio made up of the Captain, the Colonel & Sgt. Tibs (with Jasper & Horace right behind). It's interactions & conversations between personalities like these that always intrigue me. The way Sgt. Tibs is repeatedly flustered by the Colonel's serious yet awkward demeanor alway's makes me laugh. It's Leslie Nielsen if he were a sheepdog. To me, that stuff is pure gold.
& speaking of gold... isn't J. Pat O'Malley's English accent for Jasper just beautiful? Out of all the lines in the movie, Jasper has the best ones: phrases like "...We're gettin' plenty of boodle.", his long stretch about the new law passed in Parliament, & one of my all-time favorite line from any Disney film: "Here, grab a torch! We'll hunt 'em down before ou can say 'Bob's yer uncle'!"
I could probably go on & on about how great this movie is, but it'll just turn into a big gushfest, so I'll leave off here. I highly recommend buying (or at least renting) One Hundred & One Dalmatians on DVD. The bonus features may be lacking, but the film is worth the cost.