The Hitchhiker's Guide to the Galaxy Allusions

Culture and history

• "two thousand years after one man had been nailed to a tree for saying how great it would be to be nice to people for a change" (Introduction.6) is a reference to Jesus Christ
• Genghis Khan (1.17) is the famous Mongolian conqueror 
• Ford Prefect (1.55) is a type of British car
• Arsenal (2.22) is a reference to the British soccer team, though they call it football there
• The Visigoths (3.26) were a Germanic tribe, considered barbaric by some people who had stuff the Visigoths wanted
• Joseph and the Amazing Technicolor Dreamcoat and Godspell (3.62) are musicals
• Easter Island (4.7) is an island with giant stone heads
• Nelson's Column (6.29) is a monument in London to Admiral Nelson, who led the British navy to some important victories in the Napoleonic War
• Beethoven's Fifth (7.97) is a symphony that you might recognize if you heard
• Bogart (6.30) is a reference to Humphrey Bogart, the American film star
• Southend (9.21) is a British seaside town and resort
• "Hamlet" (9.81) is a play by some guy
• "to boldly split infinitives that no man had split before" (15.3) is a cheeky reference to the original Star Trek, which had a split infinitive in its opening narration: some people would prefer "to boldly go" be changed to "to go boldly"
• "When you walk through the storm / hold your head up high ..." (17.79), which Eddie sings, is from the song "You'll Never Walk Alone", originally from the musical Carousel
• The Guardian (22.36) is a left-leaning British newspaper
• "How many roads must a man walk down?" (32.10) is a reference to the Bob Dylan song "Blowin' in the Wind" 

Astronomy and other sciences

• Betelgeuse (1.52), Alpha Centauri (3.75), Barnard's Star (5.30), and Alpha Proxima (8.7) are all stars
• Goonhilly, Cape Canaveral, Woomera, and Jodrell Bank (3.2) are all different space research centers or shuttle launch sites.
• Brownian Motion (10.4) is a way to describe random motion
• The Horsehead Nebula (12.33) is this amazing nebula