Gusty Winds in Salmon of Doubt is an incarnation of Schroedinger's CatConsidering that it's a cat that's half alive (specifically, the front half), we don't know if the back half is still alive, and he passes a sign reading "GUSTY WINDS MAY EXIST"...
In Salmon of Doubt, a future version of Dirk is orchestrating the first few chapters.
Professor Chronitis is a Time Lord, and his time machine is his TARDIS.Yeah, that's right. This WMG was actually justified once. The end times are upon us.
All life in the universe is a result of a stable time loop.Life on Earth started because of an accident caused by another intelligent life form. Time travel is also possible in the Dirk Gently universe. What more evidence do you need?
Dave, from the first chapter of Salmon of Doubt, is a kangaroo.It's mentioned that the human race is extinct, and that kangaroos are being taught to speak. Perhaps the "heavily armed kangaroos" from the description brought about the death of the human race, and now rule the world?