Instead of an xkcd reference:
An RP Feynman one.
From the story called I want my Dollar in Surely you're joking Mr Feynman, available from all good bookstores.
[D]uring the war, at Los Alamos, there was a very nice fella in charge of the patent office for the government, named Captain Smith. Smith sent around a notice to everybody that said something like, "We in the patent office would like to patent every idea you have for the United States government, for which you are working now. Any idea you have on nuclear energy or its application that you may think everybody knows about, everybody doesn't know about: Just come to my office and tell me the idea."
I see Smith at lunch, and as we're walking back to the technical area, I say to him, "That note you sent around: That's kind of crazy to have us come in and tell you every idea."
We discussed it back and forth - by this time we're in his office-and I say, "There are so many ideas about nuclear energy that are so perfectly obvious, that I'd be here all day telling you stuff."
"Nothin' to it!" I say. "Example: nuclear reactor . . . under water. . water goes in . . . steam goes out the other side . . . Pshshshsht - it's a submarine. Or: nuclear reactor . . . air comes rushing in the front. . . heated up by nuclear reaction . . . out the back it goes . . . Boom! Through the air-it's an airplane. Or: nuclear reactor . . you have hydrogen go through the thing . . . Zoom! - it's a rocket. Or: nuclear reactor . . . only instead of using ordinary uranium, you use enriched uranium with beryllium oxide at high temperature to make it more efficient . . . It's an electrical power plant. There's a million ideas!" I said, as I went out the door.
About three months later, Smith calls me in the office and says, "Feynman, the submarine has already been taken. But the other three are yours."