Carmageddon!

If you don’t know about Carmageddon, then you’re not on Twitter. Or in LA.

Carmageddon happens this weekend when a 10-mile section of northbound I-405, a major thoroughfare that courses its way through the Los Angeles area, shuts down from midnight Friday to as late as 6 a.m. Monday.

Anywhere else, a freeway closure might be a minor hassle. But in car-dependent Los Angeles, it’s being dubbed Carmageddon.

That can only mean one thing: a Twitter hashtag. If you happen to be anywhere else, you might be subjected to some of the gridlock-talk on Twitter because on Friday, #carmageddon became one of the Twitter’s top trends.

Many of the tweets were simply informative (as if anyone living in LA could possibly not know about it).

But Hollywood being Hollywood, many looked at the hashtag and saw an angle to promote themselves and their wares.

Angelenos were using Twitter to pimp their stuff—everything from T-shirts to drinks to airplane flights. JetBlue is offering $4 flights between Long Beach and Burbank. That in turn gave environmentalists a chance to push their cause and chide the airline for adding to LA’s already sizable carbon footprint. Bicyclists, in turn, challenged airline passengers to a race.

And of course, the rich and famous also got in on the act, after a little prodding by the Los Angeles Police Department, which actually asked celebrities to tweet out the news—whether or not their followers, who might be all over the world, cared.

Not all the celebrities asked to tweet participated. (Lady Gaga, where art thou?) But many did. Tom Hanks, Khloé Kardashian, Nicky Hilton, Kevin Smith, and Piers Morgan  all tweeted to their massive followings about the closure. (@NickyHilton was the only one to worry about the dress code.)

Rainn Wilson also weighed in with his humorous tweet: I think ‘Carmaggedon’ is mentioned specifically in the Book of Revelations.”

 A lot of people used the event to entertain us with witticisms.

And if you’re actually in Carmageddon? There’s even a Foursquare venue. If you’re stuck in traffic, turn off your engine and check in. It’ll be a while.