Since the beginning of network television, many shows have been preceded by an announcement or theme song that served various purposes. In the 1950s and '60s, it was common for announcers to declare that a program had been "brought to you by" a sponsor who paid for the privilege of introducing a show. Other programs, such as The Twilight Zone, Star Trek, and The Odd Couple, provided a brief encapsulation of the show's subject matter, a practice that...