NASA engineer Bill Tindall was renowned within the agency for the informal tone of the incredibly important internal memos he sent during his tenure. So much so that these “Tindallgrams” have been circulating amongst enthusiasts ever since, and can be found, in PDF format, at the collectSPACE website.
Below is just one of the hundreds he sent. It was written in November of 1968, just eight months prior to the Apollo 11 spaceflight, and saw Tindall amusingly bring to light a potentially startling problem relating to the Lunar Module.
(via Letters of Note: Gee whiz, that master alarm certainly startled me)