Toontown is the only land in Tokyo Disneyland almost entirely inspired by a single movie, that movie being "Who Framed Roger Rabbit?" In the movie, cartoon characters (called "Toons") were not just drawings on a page, but actually had a life of their own. All Toons, when they were not in the studio making movies, resided in a place called Toontown. Thus is the inspiration for Tokyo Disneyland's Toontown.
You would expect a place that's home to cartoon characters to be a wacky, mixed-up place, and Toontown lives up to that expectation. Buildings are oddly shaped, signs sometimes make no sense, and everything looks like a life-size, three-dimensional cartoon. Toontown is also a very "hands-on" place; just about every door knob, lever, button, and handle you find does something or makes some sound-effect when operated.
Toontown at Tokyo Disneyland is very similar to the original Toontown at Disneyland in California, but the layout is reversed (for example, Roger Rabbit's Cartoon Spin is on the far left of Toontown at Tokyo Disneyland, versus the far right for Disneyland in California). Toontown at Tokyo Disneyland is also very, very crowded with people, even on slow attendance days (which are few).