This article was corrected on October 22, 1992. Twentieth TV exex have denied a report in yesterday’s Daily Variety speculating the subject of a sales meeting this week involved development of a marketing plan for “The Simpsons.” Although there is a marketing plan for “The Simpsons” being developed, this week’s gathering involved existing product.An expensive four-page “mystery” ad appearing in TV trade magazines this week boasts that an upcoming syndie show features a central character “profiled in the Wall Street Journal, New York Times and Washington Post.” The ad also asserts the character “changed the viewing habits of America’s adults” and that “he is a topic of study on America’s campuses.” On the final page, readers can see the back of a chair with the hidden character looking out at the bright lights of high-rises in a large Midwestern city. A hand reaches down to pour the mystery man a cup of coffee. “He’s coming soon. Watch this chair,” the ad proclaims. At first glance, it might appear to be an advertisement for an upcoming firstrun late night talkshow. Inquiring–or is it “Enquiring?”– minds may leap to the conclusion the ad is referring to David Letterman and that Twentieth Television is the unnamed syndicator. Forget it. Despite all the stories about Fox’s efforts to secure the show (either for Fox Broadcasting Co. or Twentieth TV), the disgruntled NBC late night host can’t officially sign any deals until after first negotiating with his current employer early next year. So that leaves only one other likely suspect: Bart Simpson. He’s a phenomenon who has been the topic of stories in major newspapers, who’s been studied in sociology classes and who helped siphon a number of adults away from NBC’s “The Cosby Show” when Fox Broadcasting moved “The Simpsons” to Thursday nights. Twentieth is expected to unveil its marketing plan for the show’s off-net launch in the near future. In fact, high-ranking Twentieth TV sales exex have been locked up in sales meetings and unavailable for comment ever since the secretive ad appeared on Monday. The likely topic of conversation at the strategy sesh is how to sell a show that, despite being a runaway hit in prime time, may prove to be a more difficult sell in syndication. Twentieth must devise a uniform plan of attack to deal with the likely questions from stations. Because it appeals to both kids and adults, “The Simpsons” could play in access, early or late fringe. The off-Fox show could be targeted for access slots on network affiliates in the top-50 markets, which are otherwise prohibited from airing off-net fare under the prime time access rule. But there are questions about whether major-market affils are willing to play an animated show in access. And Fox affils and indies must grapple with putting the show in with their children or adult programming blocks. The distrib also must consider the best year in which to launch the strip. With several off-net sitcoms targeted for ’93 and ’94, Twentieth could opt to wait until ’95.