Not only is Farah wearing a letter man jacket with the number 42 on it (the answer to Life, the Universe and Everything), the name Adams is embroidered on top of the letter "D", both obvious homages to Douglas Adams, the Dirk Gently and Hitchhiker's Guide creator.
When Dirk is looking for Todd and Amanda in Wendimoor, The Executioner calls Dirk a "hoopty frood." This is another reference to Douglas Adams' book Hitchhiker's Guide to the Galaxy, in which the similar term "hoopy frood" is used.
Mr Priest walks past a large cage in the Blackwing camp. Although the occupant of the cage is not shown, the Purple People Eater theme is briefly heard.
"Operation Paperclip" mentioned in the opening credits is the plan by the US government to bring 1,600 German scientists and engineers captured in WWII back to the US for government employment.
The 'rainbow monster' calls Dirk bibbit, this is also the name of a character from One Flew Over the Cuckoo's Nest (1975); Billy Bibbit. In the film Bibbit is portrayed by Brad Dourif, the father of Fiona Dourif (Bart).