Found this little nugget in the “find” man page recently:
A ‘%’ character followed by any other character is discarded, but the other character is printed (don’t rely on this, as further format characters may be introduced). A ‘%’ at the end of the format argument causes undefined behaviour since there is no following character. In some locales, it may hide your door keys, while in others it may remove the final page from the novel you are reading.
Reminds me of a T-shirt I have:
$> man woman $> Segmentation fault (core dumped)