Then a young man, who looked like he might not have been alive when “Seinfeld,” the sitcom David helped create, ended its run in 1998, took a different tack, telling David that his neighbors put up Halloween decorations in September. Leaning forward in his white swivel chair, David shouted back, “You should egg their house!” Suddenly, David perked up, excitably, gesticulating with Three Stooges physicality about the transgression of getting ready for a holiday too early. “Unacceptable,” he said, then added that they should take down the decorations the day after Halloween.