After an on-air joke by Conan O’Brien, it was fear of the fine-wielding FCC that prompted NBC to buy the domain name “hornymanatee.com.” “By yesterday afternoon hornymanatee.com — created by Mr. O’Brien’s staff and featuring images of such supposedly forbidden acts as ‘Manatee-on-Manatee’ sex … — had received approximately 3 million hits, according to NBC.” And the site’s content is coming from both the show and its viewers. ” ‘We couldn’t have done this two years ago, three years ago,’ Mr. O’Brien said. ‘It’s sort of this weird comedy dialogue with the audience.’ “