Jimmy Kimmel drew his biggest Wednesday-night (OK, technically it was Thursday morning, since the show starts at midnight) audience ever this week -- thanks to a visit from a rival, David Letterman. Jimmy Kimmel Live, which is airing this week from Brooklyn (it is usually taped in Hollywood), wound up as something of a love affair, with Kimmel showing Letterman photos of himself as an 18-year-old with the words Late Night with David Letterman on his birthday cake and a Late Night license plate on his first car. I hope I'm not making you uncomfortable, Kimmel remarked. I'm more concerned for you, replied Letterman. Did your parents step in? These are warning signs. Earlier Kimmel told Letterman that he thought Letterman's visit was perhaps similar to Johnny Carson's visit to his show in 1985. The difference, said Letterman, was that Johnny Carson was something ... and I'm not much of anything. Kimmel, of course, disagreed. This is serious for me. Letterman praised Kimmel for being generous and courteous and kind to me [during] my entire career, then said that it was all very troubling. I kept saying to people, 'Why is he sucking up to me?'