S11E10: Little Big Mom

In "The Simpsons" Season 11, Episode 10, titled "Little Big Mom," the episode wraps up with Lisa deciding to take drastic measures to get her family to start cleaning up after themselves. She concocts a plan involving a fake leprosy scare, using oatmeal and green food coloring to create fake sores on Homer and Bart. Believing they have contracted leprosy, Homer and Bart head off to a leper colony in Hawaii for treatment. While they're enjoying the luxurious accommodations, Lisa's conscience gets the better of her. She confesses the ruse to Marge, who is still recovering in the hospital. Marge quickly flies to Hawaii to bring her husband and son back home. The episode concludes with Homer and Bart still clueless about Lisa's trick, as they are too busy enjoying their time in Hawaii. It’s a classic case of “ignorance is bliss” as they bask in their vacation, oblivious to the reality waiting for them back in Springfield.