Basically all throughout the book(s), they authors use food names as variable, function names etc. It is indeed a nice idea because people do tend to associate good memories with delicious food. Especially if the food is greasy or sweet!
That quote This space is reserved for Jelly Bean stains is basically a filler sentence at the end of a chapter on a page, which happens to be high up in the page, the remainder of the page is basically empty, so they put it in as a joke.
This is not any different than the joke at the beginning of the 'Camel Book', Laziness, Impatience and Hubris, the three great virtues of a programmer.
You really should read those books, its one of those unique kinds of books that use a very innovative(albeit a very ancient) technique to teach you some very mind bending concepts. Its is possible that the approach will help you in understanding other things as well.
