At the time of filming, BBC policy was that all comedy shows should have a laugh track. The first two episodes were played to an audience of 100 people to record the laugh track, but it was never broadcast in this form.
For the original run in the United States, the six-part series was edited into seven parts (since the original episodes all ran over thirty minutes and could not fit into the rigid 30-minute time slot). An interesting sidenote to this is that when the six 35-minute episodes were made into seven 30-minute episodes, the plot recap intended for the beginning of each episode appeared five minutes later in the program with each subsequent installment (and did not appear at all in the final episode!) After this version was televised on PBS stations a few times, the program disappeared from American airwaves for a while. Then the original version, with its six slightly overlong episodes, showed up, and that's all that's been seen on public TV since.
Several different versions of the series survive on video. It was originally made as a six-episode BBC TV series (based on 'Douglas Adams''s radio scripts) but for the video cut was re-edited in places. The HHG was done on two SP tapes and also on one large SLP/EP tape. The SLP/EP runs continuously (though subtitled "Part One") and is cut into a sort of "movie." The ends of episodes are sometimes hard to distinguish, except in a bad cut toward the end where Arthur says "Mice?" and the music climaxes then cuts abruptly. The SP version comes in two parts and seems to come in both the unedited episodes and the "movie." All of these differ in some ways from the original broadcasts. Scenes like the one in the Vogon Airlock were cut from some re-broadcasts; they appear here. Other scenes "previously unaired" include Arthur and Ford searching for Slartibartfast's signature on a glacier and only appear on a few versions.
The first episode, when it was shown to a live audience for the purpose of recording a laugh-track (see above) included an 8:30 comedic video introduction by series narrator Peter Jones. This sequence was never broadcast on TV, but has been included as an extra on the Warner Brothers DVD release.