Let’s begin by looking at Ray Bradbury’s story “A Sound of Thunder” which was first published in 1952, a few days after I was born.
In the year 2055, time travel to the past is available as a form of big game hunting. To ensure that killing a dinosaur doesn’t change history, the guide researches a path in advance to identify a target animal that historically died by accident shortly after the planned moment of arrival.
However, during one trip, the hunter panics at the approach of the designated T. Rex and steps off the path, accidentally crushing a butterfly. When the hunter and guide return to 2055, they discover that certain words are now spelled differently and the “fascist” candidate who had lost the recent presidential election is now the winner.
https://en.wikipedia.org/wiki/A_Sound_of_Thunder
The notion that a small disturbance can become magnified through time and change the future significantly dates back at least as far as an 1800 publication by the German philosopher Johann Gottlieb Fichte. Modern discussion refers to this phenomenon as The Butterfly Effect, based on a metaphor used by meteorologist Edward Lorenz in the 1960s to explain why small changes in his weather model could produce very different atmospheric effects.
https://en.wikipedia.org/wiki/Butterfly_effect
Now consider Tarantino’s two films Inglourious Basterds (2009) and Once Upon a Time…In Hollywood (2019). In the first of these, Adolf Hitler is assassinated; while in the second, Sharon Tate’s murder is prevented. The most popular explanation for these happy endings is that Tarantino is presenting an alternate history. This theme has been explored at length in recent fiction, such as the TV series The Man in the High Castle which began broadcasting in 2015 based on the 1962 story by Philip Dick.
What does the odd spelling of Inglourious Basterds signify? Tarantino has repeatedly refused to give a clear explanation of why he changed the spelling of the English title of the movie that had inspired him: Enzo Castellari’s 1978 film The Inglorious Bastards.
I surmise that the spelling is not odd: it is standard in the parallel world in which Tarantino’s war movie is set. Similarly, we can view anachronisms in Once Upon a Time…In Hollywood as evidence of a parallel world.
What’s the difference between an alternate history and a parallel world? An alternate history is a fictional device for projecting how our world would be different if history turned in a different direction at a significant fork in the road. For example, if the Allies had lost ww2, an America similar to that shown in The Man in the High Castle could result. The writer imagines what might happen after the turning point.
Although a parallel world might split off from ours at the point where the alternate road was taken, the notion of parallel world is broader in scope than alternate history. A parallel world could have diverged from ours before the story’s events began. For example, words might be spelled differently.
Inglourious Basterds does not portray a historical assassination team that succeeds in contrast to its failure in the real world (e.g., the 2008 movie Valkyrie). It imagines a unique team and the plot has twists that make the movie great. However, the notion of “alternate history” as a divergent path only applies in a generic way: somebody assassinated Hitler and presumably the world will then be better off (but Tarantino leaves that future to our imagination).
Once Upon a Time…In Hollywood thwarts the murders of August 1969 through a succession of ordinary actions and reactions that divert the Manson Family members away from their nefarious plan, leading them toward a confrontation with people who are capable of defeating them.
Tarantino’s period piece about Hollywood doesn’t have any odd spellings (other than “Racquel Welch” on a drive-in marquee), but it has plenty of cultural and technological anachronisms. There are so many that one wonders if they’re all simply due to the production research team being overloaded and getting confused about release dates.
https://www.imdb.com/title/tt7131622/goofs/?tab=gf&ref_=tt_trv_gf
The simplest errors seem to involve identifying an artifact’s year but not its correct month. For example, a Pan Am 747 jet brings Sharon Tate and Roman Polanski to LA in February 1969, then takes Rick Dalton and Cliff Booth back from Italy in August. The 747 was tested early in 1969, but it wasn’t certified until December and its first commercial flight was in January 1970.
When Sharon stops her stroll in front of a movie theater that is playing a movie she starred in recently, the camera shows that Pendulum is playing in the theater across the street. However, that film was released in March 1969, a month after it appears on the marquee in Tarantino’s movie.
A bigger divergence is revealed by a Coming Attraction poster that appears before Sharon goes inside the theater. It advertises The Mercenary, a spaghetti western released in Italy in December 1968 but not shown in US theaters until March 1970, a full year after her day at the cinema. This seems extraordinarily far in advance for a Coming Attraction poster.
We can also hear Joe Cocker’s cover of “The Letter” playing on a car radio even though he didn’t produce that recording until 1970. The mismatch of the timing of this song and the two aforementioned films could be goofs in production. Or they could be hints that artistic production in the parallel world didn’t always occur at the same pace as in our own world.
Anachronisms in language might also be due to sloppiness in the script — or perhaps additional hints about cultural differences in the parallel world. For example, the flippant use of “Whatever” and the directions guiding Rick to the make-up trailer: “Straight back the way you came, hard right.” The idiom “hard right” didn’t appear in our world until decades after 1969.
I found this film particularly enjoyable because I remember many of these cultural artifacts from my youth. Tarantino assiduously made the movie’s setting as authentic as possible by means of billboards, cars, clothing, hair styles, songs, dance moves, etc. Reproducing Hollywood in 1969 was an immense task and he can be forgiven for a few dozen goofs.
Or maybe they aren’t goofs, and he’s trying to show us something other than an alternate history?
BONUS commentary: Why does the title have an ellipsis (…) at the end of the movie?
The phrase “Once Upon a Time” in a movie title has become a meme in the last three decades or so, mimicking the pattern of Sergio Leone’s Once Upon a Time in the West (1968). An ellipsis causes a reader to pause. In this case the pause is a hint that “In Hollywood” is not just another location like “In America” or “In China” or “In Mexico”.
The phrase “Once upon a time” is a well-known opening for a fairy tale, which a fictitious movie generally is. Hollywood differs from the other places in the films that have a “Once Upon a Time” title because it is a place that generates fairy tales. In other words, this movie about Hollywood is a fairy tale about the making of fairy tales. Tarantino is using recursiveness to push us to a higher level of contemplation, more subtle than the self-referential easter eggs he is fond of inserting each time he makes a movie.