Surely the inspiration for the invention of the Palm Pilot,
as well as being the show that convinced a generation of backpackers it was vital to
pack a towel.
Douglas Adams' story was about what happens to the last living human
after the earth is blown up to make way for an interstellar bypass.
It was hugely successful on radio, and as a novel, and was remade for television
featuring a largely unchanged cast, plus a rather dubious-looking
animatronic model head.
The series became a massive cult hit and the BBC has since built
its own guide to life, the universe, and everything - H2G2.