Punch Lines

By George: The Star says JFK Jr. and wife, Carolyn, are having trouble conceiving, possibly because of stress. “To excite him, Carolyn is planning a real Kennedy weekend: She’s taking him to Chappaquiddick, dressing like Marilyn Monroe and ‘baby-sitting’ him.” (Bill Williams)

1-800-USA DERAIL: Japan has built a train that goes 329 mph by floating a fraction of an inch above the tracks. “Forget speed. I’d be happy if Amtrak could just keep its trains that close to the track.” (Steve Voldseth)

But Didn’t Ali MacGraw’s Character Die at the End? Vice President Al Gore recently hinted that the star-crossed couple in “Love Story” was modeled after him and his wife. “Later, Gore said he was mixed up, and that he and Tipper were actually the inspiration for the film ‘Coma.’ ” (Premiere Radio)

How About ‘The Blob’? “Meanwhile, actor Tom Arnold claims that the main characters in ‘Titanic’--the boat and the iceberg--were inspired by his ex-wife, Roseanne.” (Roy Rivenburg)

Term Limits: South African President Nelson Mandela says he’ll step down when his term ends in 1999. He spent 25 years in prison before holding public office. “In America, we do it the other way around.” (Argus Hamilton)

Things Go Better: A USA Today poll says 86% of kids think the coolest Christmas gift would be a Coke machine in their bedroom. “When Robert Downey Jr. was asked the same question, he wanted a coke dealer in his bedroom.” (Premiere Radio)

Santa’s Sweatshop: Fidel Castro is allowing his Cuban workers to celebrate Christmas for the first time in 28 years. “No word from Kathie Lee Gifford on hers.” (Voldseth)

The Buddy System: “People are wondering why the president got a puppy. Some say it’s to replace Chelsea. But the real reason, as all men know, is because dogs are babe magnets.” (Paul Steinberg)

*

The Abridged David Letterman:

Top 10 signs your wife is having an affair with Santa Claus . . .

10. She refers to your bed as “Santa’s Workshop.”

7. She smells like a combination of peppermint sticks and reindeer chow.

5. Paramedics need Jaws of Life to get the two of them out of the chimney.

4. Lately, she’s been commuting to work in a flying sled.

* SEND US A LINE: Got a joke? Send it to Laugh Lines by fax, (213) 237-0732, or mail, Life & Style, Los Angeles Times, Times Mirror Square, Los Angeles, CA 90053.