A mere 33 years ago today — Oct. 12, 1979 — the first novelized version of The Hitchhiker’s Guide to the Galaxy was published. Despite beginning life as a rather popular BBC radio series, it was the prose incarnations of Douglas Adams’s Hitchhiker’s Guide series that cemented both his and its place in not just geek lore, but mainstream culture at large.

The Hitchhiker’s Guide novels have been translated into over 30 languages. They’ve been adapted into video games and stage plays. The original radio plays have been broadcast throughout the English-speaking world. The BBC commissioned a well-regarded television miniseries based on Hitchhiker’s Guide that remains available today. For frak’s sake, there are still two active USENET groups dedicated to Douglas Adams and the Hitchhiker’s Guide universe, to say nothing of sizable portions of the ThinkGeek catalog.

Yet, for all that popularity, it still took 25 years to realize a major motion picture version of The Hitchhiker’s Guide to the Galaxy. The movie was in proverbial “development hell” for 20 years and wasn’t produced until after Douglas Adams’s death. Nonetheless, his influence on the film is substantial — Adams wrote several early drafts of the script — and may explain why he made a special effort to secretly tie the Hitchhiker’s movie universe into another well-known science-fiction franchise.

WHAT OTHER MAJOR SCI-FI FRANCHISE “SHARES” A UNIVERSE WITH THE HITCHHIKER’S GUIDE TO THE GALAXY?

Get the answer.

According to The Hitchhiker’s Guide to the Galaxy movie, it’s entirely possible that a certain Gallifreyan Time Lord could someday find himself at the Restaurant at the End of the Universe, as Hitchhiker’s shares a universe with Doctor Who.

Warning, very mild spoilers ahead.

When Arthur Dent is touring the Magrathean planet assembly line in the Hitchhiker’s Guide film, the prison planet Shada is visible on the factory floor. “Shada” was the title of a 1979 Doctor Who serial that was never aired due to a BBC strike. The series was written by Douglas Adams. The BBC eventually released the incomplete Shada storyline on video, with the “ending” performed via narration by Tom Baker, who portrayed the Fourth Doctor.

(Yes, Douglas Adams wrote for Doctor Who. He also wrote for Monty Python and played guitar with Pink Floyd. It’s entirely possible his untimely demise was due to an overdose of self-generated awesome.)

To double down on the time-space crossover, characters and settings from another Adams-cowritten Doctor Who serial, “City of Death,” appear in Adams’s other famous comedy novel series, Dirk Gently’s Holistic Detective Agency. It seems wherever Douglas Adams’s fiction went, the Doctor was sure to secretly follow.

That’s not just some Time Lord-entangling text twisting; it’s a fandom-friendly flash of Geek Trivia.