The wardrobe crew were shocked to discover, halfway through filming, that only one dressing gown had been purchased for Arthur, and the line had been discontinued by the manufacturer. The cast and crew were then ordered to be particularly gentle with the dressing gown for the remainder of production. Towards the end of the series, it was rumoured that a second series would be made, and when shooting wrapped the dressing gown was locked away to preserve it in case it would be needed again.
Douglas Adams chose 42 as the Ultimate Answer of Life, the Universe, and Everything simply because he thought it was the funniest-sounding of all two-digit numbers. "A completely ordinary number, a number not just divisible by two but also six and seven. In fact it's the sort of number that you could, without any fear, introduce to your parents."
At the time of production, BBC policy required all television comedy to have a canned "laugh track". Before its broadcast debut, Episode #1.1 (1981) was screened to 100 science fiction fans (with laugh track and a rather amusing introduction by Peter Jones). Armed with the fans' feedback, Douglas Adams and Alan J.W. Bell were able to convince BBC executives to change the policy, and the laugh track was removed before broadcast.
The original concept came to Douglas Adams in the early 1970s whilst backpacking around the continent with a copy of "The Hitch Hiker's Guide To Europe". He found himself lying drunk in a field in Innsbruck, looking up at the stars. He decided that someone should write a Hitch Hiker's Guide to the Galaxy; several years later he would remember the idea and write a BBC radio show around it. Later in life, Adams said that he had related the "drunk in a field" story so many times in interviews that he had lost all memory of the actual event, and simply repeated the anecdote verbatim.
David Dixon was cast primarily because he had a serious face, but "weird" eyes. It's nearly impossible to see in the film, but he wore *purple* contact lenses while playing Ford, to make his eyes look even stranger.