"Natural Born Kissers", also known as "Margie, May I Sleep With Danger?", is the twenty-fifth episode of Season 9. It originally aired on May 17, 1998. The episode was written by Matt Selman and directed by Klay Hall.
When their anniversary dinner is a flop and their love life seems too lack luster, Homer and Marge try to spice it up, first by traveling to a bed & breakfast. Meanwhile, Lisa and Bart use Grampa's mine detector to find treasure and they find an alternate ending to "Casablanca." Homer and Marge discover that the fear of getting caught is the spice they need until they are caught baring it all.
It is Homer and Marge's eleventh wedding anniversary and Grampa does not arrive at the Simpsons house to babysit the children (because he mixed up the Flanders house with the Simpson house and ended up babysitting Rod and Todd Flanders by mistake). As a result, they decide take Bart, Lisa, and Maggie to a fancy restaurant with them. However, Bart objects and takes the family to a family restaurant shaped like an airplane, called the Up, Up and Buffet!, which spoils Homer and Marge's plans for a romantic evening together. Later that evening, Homer and Marge attempt to have sex, but lack enthusiasm. The following day, it is discovered Homer left the freezer door open after thinking that the couple on the remaining slice of their wedding cake had little parties at night, causing the refrigerator motor to burn out. Homer and Marge make their way to a hardware store to buy another motor, but the car gets stuck in the muddy driveway in the middle of farm country. Meanwhile, Bart and Lisa stay at the Springfield Retirement Castle with Grampa, and they discover a metal detector in his closet. Using the detector, they use they uncover a suppressed, happy ending to Casablanca, in which Ilsa Lund and Rick marry. The Old Jewish Man steps forward to reveal that in his younger days, he was a studio executive that had tacked that happy ending onto the picture. He then gives Bart and Lisa $20.00 to rebury it, along with another film reel labeled "It's a Wonderful Life: Killing Spree Ending."
Homer and Marge rush into the nearest barn to avoid a sudden storm. A farmer discovers the barn door is open and suspects trespassers. He enters the barn, nearly catching Homer and Marge, who are hiding in the hay loft, but leaves after failing to locate them. When the coast is clear, Homer and Marge have inspired sex in the hay loft. They think their marriage has been recharged and go for a romantic weekend at a Bed and Breakfast, but soon fall into their old patterns. However, a maid walks in on them and they conclude they are both aroused when they risk being caught during intimate moments.
Their love life is recharged and one day they begin to make love on the same miniature golf course windmill where Bart was conceived. This time they come too close to being caught after Moe was almost going to gas them out, and while they manage to escape, they have to flee through Springfield in the nude after stealing Gil's hot-air balloon, which he had been living in. The balloon finally lands in a football stadium while a game is in progress, and hundreds of people take photos of Homer and Marge standing naked on the field. They end up appearing in the local newspaper under the headline "Local Couple Bares All!", accompanied by plenty of pictures.
"Natural Born Kissers" was the first episode written by Matt Selman, who partly based it on his parent's marriage. The episode was the only time that Mike Scully ever got a call from Fox where they suggested not doing the episode. They were worried about the sexual content and how it was going to be handled. It was the first episode to ever receive an M (15+) rating in Australia. (Though the episode is rated PG on the Season 9 DVD). They disliked several of the phrases used in the episode, such as the term "ass forkin'". In an interview, Matt Groening said "The network censors couldn't believe it, and neither could I: the cow at the peephole while Homer and Marge make love in a hayloft; neighbors groping Homer when he and Marge are caught nude inside the windmill at the Sir Putts-A-Lot mini golf course; Homer dangling naked from a hot-air balloon, his ass dragging against the glass of a Crystal Cathedral-like church." The producers fought the censors and in the end, very little of the script was changed. Marge's butt is also shown on television for the first time. Marge and Homer in the golf course is a reference to the season 3 episode "I Married Marge", although in that episode they are in a castle, rather than a windmill.
The idea for the episode's couch gag came from Dan Castellaneta's daughter, who was given a special credit for it.
Matt Groening listed the episode as being his eighth favorite episode, and the aroused cow is one of his all-time favorite act break jokes. The authors of the book I Can't Believe It's a Bigger and Better Updated Unofficial Simpsons Guide, Warren Martyn and Adrian Wood, called it "a superb episode which actually makes Marge and Homer's love life seem very real; everyone needs a bit of spice now and again, and they find theirs. The balloon trip is hysterical, and the attempts to explain their behavior.