For the first time in a long time, the kids were out of the house for the night. Homer and Marge could use the house however they wanted.
Marge has always been turned on my posing nude. She first posed for a charity calendar, which led to posing for Playdude and other magazines.
Homer knew that Marge is a sloppy drunk. With a bottle of wine, she loses control and will do anything--especially anything in front of a camera.