When Homer is given a Joe DiMaggio rookie card by an oblivious-to-its-value Burns, he sells it for a pile of cash. He spends most of the money on himself, only coming to realize his greedy ways when he sees "A Christmas Carol" on TV.
Homer reverses course and starts to do favors for everyone he can, in-so-doing making Flanders jealous for becoming Springfield's new king of being nice. He and Flanders engage in a "nice-off," each trying to outdo the other to earn the town's praise. Their feud escalates to ridiculous proportions.