WARNING: Do not even attempt this puzzle unless you are a dyed-in-the-wool Hitchhiker's Guide fan: otherwise only about 15% of the clues will make any sense whatsoever.
This is a slightly edited revision of a puzzle published in the October 2015 issue of Mostly Harmless (the magazine of ZZ9 Plural Z Alpha – the Official Hitchhiker's Guide to the Galaxy Appreciation Society).
Many of the clues pertain to characters and situations seen in the books, radio series and TV series. My clueing style has, I hope, improved since then, but I have only edited the clumsiest ones.