I love moments like this in any project really. Working on high stress projects with the most professional people, eventually someone is going to break and do something childish. Mostly putting cats into production code or some secret code to show as inside joke to your relatives to prove your existence and work
Personally I haven't seen anything to the levels of sneaking a sandwich into space, but I can't wait experience it, or execute it :)
This sandwich is memorialized in a resin display at the Gus Grissom Memorial Museum in Mitchell, Indiana.
A little more info about the incident, including who bought the sandwich and from where, whether permission was given, and how NASA and congress felt about the matter:
I thought someone had cornered the market for beef sandwiches in space.
John W. Young on his rookie mission. Severe official disapproval, but of course he went on to a total of six launches, two of them moonbound, two of them truly pioneering, and only relatively recently retired from NASA.
Autobiography Forever Young recommended.