The New Addams Family (1998)

S1E18 The Winning of Morticia Addams

Fester stumbles upon an article by Dr. Pierre LeBlanc called "The Dangers of a Happy Marriage" and decides to get the family involved in stirring up conflict between Gomez and Morticia. When his attempts fall flat, he contacts Dr. LeBlanc, who arrives with the intention of enticing Morticia away from Gomez. In response, Gomez issues a challenge to Dr. LeBlanc for a duel to defend his marriage.