Infocom sold an "I Got the Babel Fish" T-Shirt as a merchandising tie-in. Getting the Babel Fish was a notoriously difficult part of the game.
You can get footnotes when playing. This was the first game to use footnotes. These are how to get them:
Footnote 1 RELAX or ENJOY THE DARKNESS in Dark Footnote 2 Call your home a house while talking to Ford Footnote 3 Upon arrival at the Presidential Speedboat Footnote 4 Listen to the music in the Pub several times, until "Hey Jude" is the song that is playing Footnote 5 Remove the towel in the Beast's Outer Lair after the Beast has gone to sleep Footnote 6 Type FOOTNOTE without any number after it to see where this footnote is referenced Footnote 7 Shoot the Beast three times with the anti-Beast gun Footnote 8 Consult the Guide about fluff Footnote 9 Get the Guide entry on SPACE by having the Guide with you when you're blown out of the Airlock Footnote 10 When the game finally gives in and describes the Engine Room Footnote 11 This footnote is not referenced anywhere in the game Footnote 12 This footnote is referenced only by itself Footnote 13 Push the boat's autopilot button three times Footnote 14 When Ford hands you the Guide in the Vogon Hold Footnote 15 Read the banner at the Dais
Footnote 1 RELAX or ENJOY THE DARKNESS in Dark Footnote 2 Call your home a house while talking to Ford Footnote 3 Upon arrival at the Presidential Speedboat Footnote 4 Listen to the music in the Pub several times, until "Hey Jude" is the song that is playing Footnote 5 Remove the towel in the Beast's Outer Lair after the Beast has gone to sleep Footnote 6 Type FOOTNOTE without any number after it to see where this footnote is referenced Footnote 7 Shoot the Beast three times with the anti-Beast gun Footnote 8 Consult the Guide about fluff Footnote 9 Get the Guide entry on SPACE by having the Guide with you when you're blown out of the Airlock Footnote 10 When the game finally gives in and describes the Engine Room Footnote 11 This footnote is not referenced anywhere in the game Footnote 12 This footnote is referenced only by itself Footnote 13 Push the boat's autopilot button three times Footnote 14 When Ford hands you the Guide in the Vogon Hold Footnote 15 Read the banner at the Dais
There are "feelies" that go with the game. These include: fluff, order of destruction for Arthur's home, order of destruction for Earth, and, obviously, no tea.
The Hitchhiker's Guide to the Galaxy appears in the book 1001 Video Games You Must Play Before You Die by General Editor Tony Mott.