It is known that Quentin Tarantino and Robert Rodriguez have a special relationship. As is evident by Tarantino's appearances in Rodriguez' movies and by Grindhouse - their co-directed double-feature.
Is the title of Once Upon a Time in Hollywood some kind of a reference or homage to Rodriguez' Once Upon a Time in Mexico? Or is it just a fun way to capture the time-capsule feel of the movie, sending us back to another point in time? Or is it something else completely?