The Simpsons (1989): Season 23, Episode 21

23 - 21: Ned 'n' Edna's Blend

When the town of Springfield discovers that Ned and Edna have secretly gotten hitched, Marge offers to throw them a congratulatory reception. However, bringing everyone together makes them all realize that no marriage is perfect. Meanwhile, Edna tries to help Ned's children become more socially acceptable by changing some of the rules.