Bart became so associated with Fox that, when bidding in 1993 to show pro football, the network had to assure the NFL and reporters that the character would not announce games. Due to the show's success, over the summer of 1990 Fox decided to switch "The Simpsons"' timeslot so that it would move from 8:00 p.m. ET on Sunday night to the same time on Thursday, where it would compete with "The Cosby Show" on NBC, the number one show at the time. Through the summer, several news outlets published stories about the supposed "Bill vs. Bart" rivalry. The August 31, 1990 issue of "Entertainment Weekly" featured a picture of Bill Cosby wearing a Bart Simpson T-shirt. "Bart Gets an "F"" (season two, 1990) was the first episode to air against "The Cosby Show", and it received a lower Nielsen rating, tying for eighth behind "The Cosby Show", which had an 18.5 rating. The rating is based on the number of household televisions that were tuned into the show, but Nielsen Media Research estimated that 33.6 million viewers watched the episode, making it the number one show in terms of actual viewers that week. At the time, it was the most watched episode in the history of the Fox Network, and it is still the highest rated episode in the history of "The Simpsons". Because of his popularity, Bart was often the most promoted member of the Simpson family in advertisements for the show, even for episodes in which he was not involved in the main plot.