Drunk Girls Who Signed Waivers is a porn movie.
Homer bought the DVD of the movie for the nuclear regulators on the raft trip. However, he mixed it up with The Diversity Kittens on Meltingpot Mountain, that he had bought to keep his children happy. He hadn't noticed it until one of the regulator disliked the Diversity Kittens. Meanwhile, Bart was watching Drunk Girls. Homer quickly swapped the DVDs, let Bart to watch the Diversity Kittens.
A naked woman, with a black rectangle though her chest, is on the beach, asking the viewer if he wants to see what is under the rectangle.