We've probably all heard about one "viral" Internet phenomenon or another over the past few years -- the Star Wars Kid, the "I Kiss You" guy, the Tron costume guy, the Diet Coke and Mentos video, Lonelygirl15, and so on. Each time, the virus seems to take less and less time to sweep through the Web, infecting everyone in its path. And companies everywhere are trying to figure out how to manufacture that kind of phenomenon. The short answer, of course, is that you can't. They just seem to emerge, for reasons that are often difficult to explain.

Take the "horny manatee" phenomenon, for example. It seems that the Late Night Show was doing a skit on December 4 -- involving bizarre sports-team mascots -- in which a guy at a computer watched someone in a manatee costume dancing to a suggestive song called I Touch Myself. At the end of the skit, host Conan O'Brien made a crack about the guy going to a website called www.hornymanatee.com.

According to a recent story in the New York Times, this set off alarm bells at NBC. Why? Because staffers for the show -- and the CBS lawyers whose job it is to think of such things -- started to think about what would happen if someone set up a porn website at hornymanatee.com (an address that Conan O'Brien apparently made up on the spot). Would NBC be liable because it gave out the URL on the air?

So the quick-thinking network types registered the domain themselves and the show created a gag website about risque manatees. In less than a week, the site had received more than 3 million visitors. That in turn set off a wave of contributions from viewers, who have been sending in stories about manatees and even poetry (which has been read on the air by the Late Night host). "We couldn’t have done this two years ago," Mr. O’Brien said. “It’s sort of this weird comedy dialogue with the audience."

And people say the Internet isn't good for anything.