For the next few hours or days (or..?) all hell can break loose on Twitter, as a little hole was opened that makes it possible for greater-than-140-character tweets to break out into the wild.  

Here's an example of a fat tweet so you can see what it looks like.  

And here's a screen shot in case at some point in the future that gets truncated (as it seems likely it will). 

Here's how it works. 

1. Twitter has a new url-shortener, called t.co. 

2. When it displays a tweet with a url that was shortened by t.co, it expands the url, so you get to see the url it is pointing to. That way you know in advance where you're going. This is a good thing, it's one of the nice things about the web that url-shortening screws with. 

3. But t.co doesn't check to see that the thing you're shortening is actually a url. You can shorten things that aren't. 

4. t.co doesn't have a 140-character limit for urls. 

5. So when it shows the full url, it shows as many as were there. Even if there were more than 140, and even if it wasn't a url. 

6. Heh.  

Update: I whipped up a little web app to show how it works.