"Ned 'N Edna's Blend" is the twenty-first episode of season 23.
Ned and Edna announce that they secretly got hitched, so Marge throws a wedding party for them. But marriage invites trouble when Edna consults Bart, so Edna 'improves' Rod and Todd's lives.
At the beginning of the episode, townspeople are auditioning for the Passion Play, based on the life of Christ. Ned Flanders auditions for Jesus, but when he is turned down by the producer, after listening in, Homer plans to audition, and he gets the role of Jesus. Ned is startled at this result. Homer goes home and after his annoyance that he has a line in every scene, he learns his lines and the play is a success. After Ned offers an apology to God for being a 'doubting Thomas' the cross on which Homer is on breaks and falls on top of Ned. Then Ned is carted off to an ambulance, Edna steps in with him and the paramedic tells him "close family only", Ned tells him that she is his wife, revealing that he and Edna are married.
At the hospital, half the town intrudes on Ned's room, and Edna tells everyone to clear out. Marge plans to establish a wedding party for them, something which Helen Lovejoy is extremely unhappy about. They soon realize that having an "open" marriage, as Ned calls it, is tricky, and they have to deal with the ups and downs. While at dinner they witness Bart next door yelling out to Homer "get his fat ass over to the flander's" Homer, in his underwear angrily asks Bart to stop calling him that. Bart cheekily asks "which one Homer or Fatass?" Homer gets outraged and shouts Why you little they're both bad and I suspect you know it" and strangles Bart. Bart, while getting strangled yells at Homer to get his hands off him and calls him a fatass. Meanwhile, after an argument with the head, Edna pulls Rod and Todd out of Christian private school and into Springfield Elementary.
Later, she takes some advice from Bart and tries to turn them into regular kids, to some success. Ned worries about Todd going to college, which is filled with classes and other topics he hates. There is a sequence entitled Ned's Nightmare, where he dreams that his kids will major in comparative religions. At their wedding party, Ned gets very upset with Edna, due to comments by Rod and Todd, something which Helen Lovejoy captures on her phone. However, Homer and Marge orchestrate a charade in front of Ned, in which they have an argument over Bart and Lisa. Realizing that all couples disagree over their children, Ned chooses to forgive her.