The now-famous Keep Calm and Carry On poster was produced by the British Ministry of Information in 1939, as a quintessentially British statement of what to do in the event of German invasion. The poster actually wasn't circulated at the time, and only became popular after its rediscovery at a bookstore. Among my friends, it's something of a mantra -- I know one woman who has the phrase sewn into the lining of her coat.
But enough with boring history. Let's look at some wacky variations on the poster that have appeared online. Tip for nerds: a lot of these are available as prints (and notebooks, phone covers, mouse pads, you name it) from various online vendors. Google it.
I first saw this on a whiteboard at a software company. Get Commissioner Gordon on the phone!
For all the hoopy froods in the house.
Everyone knows The Thing can only be killed with fire. Also: winter is coming.
Mario or Zelda? You decide.
She'll want to hear what's up.
This is what you do if Mom isn't picking up.
A spot of tea always helps.
Necessary advice for the coming zombie apocalypse.
Useful while you're waiting for that damn Sorting Hat to figure you out.
Easy for you to say, Gandalf!
Oh, internet. How self-aware you've become!
There are zillions more in a Flickr pool devoted to this sort of thing.