Keep Calm and Carry On was a poster produced by the British government in 1939 during the beginning of World War II, intended to raise the morale of the British public under the threat of impending invasion. It was little known and never used. The poster was rediscovered in 2000 and has been re-issued by a number of private sector companies, and used as the decorative theme for a range of other products. There are only two known surviving examples of the poster outside of government archives
I found it entertaining. It is an easily modified meme, and it’s in the public domain:
Parodies of the poster, with similar type but changing the phrase or the logo (for example, an upside-down crown with “Now Panic and Freak Out”), have also been sold. The poster’s popularity has been attributed to a “nostalgia for a certain British character, an outlook” according to Bagehot, a reporter for The Economist, that it “taps directly into the country’s mythic image of itself: unshowily brave and just a little stiff, brewing tea as the bombs fall.” Its message has also been felt relevant to the late-2000s recession and has been adopted as an unofficial motto by British nurses, the poster appearing in staff rooms on hospital wards with increasing frequency throughout the 2000s. Merchandise with the image has been ordered in bulk by American financial firms, advertising agencies, and by Germans.