It follows the same 2 titular characters over the course of 3 acts. In the 1st act, they're minstrel show characters who become self-aware, and decide to make money for themselves. So in the 2nd act, they're hip-hip superstars, but they get swept up in the gaudy lifestyle (though one of them is more activism-minded, while the other is more revenue-minded). They begin to get involved in some questionable enterprises. And.....I wont spoil the 3rd act.
But even that description doesn't really do justice to the play. It's very self-aware, very meta, with no 4th wall. And it's much more complicated than the summary above reflects.
The design changes for each act, as each one has a totally different setting. But the most striking design is in the 1st act - with a kind of sunny, grassy meadow that's deliberately made to look fake and cartoonish.