He may have retired from the galaxy far, far away after he sold his company for $4 billion in 2012. But Star Wars creator George Lucas has his fingerprints all over the latest movie in the Disney-Lucasfilm canon — according to his friend, Solo director Ron Howard.

Not only did Lucas come up with the idea for a Han Solo spin-off first — long before Rogue One was a thing — but he was there on set to offer advice on how his creation would behave. And he even tried his hand at acting: pitching one scene, "he played Han Solo," Howard says.

In a wide-ranging interview with Mashable, Howard also recalled how Lucas first told him about Star Wars on the set of American Graffiti in 1972, explained why the look of the film is a homage to Lucas' signature style, and dangled the possibility that Lucas could return to direct more Star Wars films — if the fans wanted.

Here's our Q&A, which has been edited for length, clarity and the removal of spoilers.

Mashable: One of my first responses to seeing Solo, and I mean this in the best possible way, was: it's the dirtiest Star Wars ever.

Ron Howard: Good! That sort of visual honesty was really important to the cinematographer, Bradford Young. I really agreed with it. The idea that really hooked him was that he could shoot some of this in [1971 Western] McCable and Mrs. Miller style. I was thinking of gritty, existential 1970s car movies like Bullitt and Vanishing Point.

M: That was George Lucas' breakthrough with Star Wars; he talked about the used universe, making space feel lived-in. Did you feel like you were kind of dropping the mic on the used universe? Like, it can't get more used than this.

RH: [Laughs] Well, the more you begin to really drill down on the way of life and the characters — and this is probably the most character-driven of the movies. I mean, it's not an epic war story. It's not political. It really is: how do these relationships impact Han?

The more up close and personal we get with the characters, the more used the universe is going to feel. It's those details about how things really work — that's the stuff prop makers and set designers just love to explore. They pull out references from different corners of our Earth and find ways to adapt them.

M: Were you there saying "throw more mud at that Wookiee?"

RH: Oh yeah, that was part of the promise of this. As action adventure movies go, I always loved Road Warrior. And while there's nothing post-apocalyptic about Solo, we are in a lawless time. Some of it takes place in frontier towns. [Han's homeworld] has this grimy port culture with a seedy underbelly. That grime is part of what's interesting about this movie.

Ron Howard and George Lucas on the set of 'American Graffiti' (1973). Image: Universal

M: Let's go back to American Graffiti. I've talked to other actors on that movie and they have these varying memories of what George was saying about Star Wars, his next movie at the time. Do you remember that?

RH: Well he wasn't very talkative in general. It only came up once in conversation, and I initiated. I said, "what do you think you're going to do next?" He said, "well, I kind of like this science fiction, maybe like Flash Gordon or Buck Rogers. But instead of bad special effects and wires and dangling spaceships, I want to do what Stanley Kubrick did, and apply that technology from 2001 to an action movie.

And that was it, the conversation died. It didn't sound very good to me. But five years later, when I went to see the movie at the Chinese Theater as a paying customer, my wife and I came out of the theater completely blown away. And without saying much of anything, we just got in a two-hour line to see the movie again. We saw it twice that day.

M: George said this thing in 1977, to Rolling Stone: he was going to get all his friends to direct Star Wars movies, and then he would come back and do the last one to show them how it's done. But you're the first example of that.

RH: He did float the proposition before. When he was getting ready to do [the prequel episodes] I, II and III — we'd worked on Willow together and I was visiting him in Marin County. He said I think the [CGI] technology is there [to do more Star Wars movies], would you like to do one?

There was no script. It was no kind of concrete offer, it was just a theoretical question. I said, "no, I don't think I ever would, George, I think you should do it." Turns out he did ask Steven Spielberg, Bob Zemeckis and a few others the same question, and at that point we all told him he was the only one who could tackle it.

But now that it's broadening out, it's become a really inviting proposition. The interesting thing to note here is the origins of [Solo] came before Disney acquired Lucasfilm. I didn't know that, I just knew I really liked the script and thought I could bring something to it and was excited to try. But it makes a lot of sense to me that this wasn't the result of some studio directive.

This came from [screenwriter] Larry Kasdan talking to George Lucas, with [Lucasfilm president] Kathy Kennedy in attendance, saying: what are the very best stories we can tell that would mean the most to fans?

M: So if Solo is a success, George might be tempted to come out of retirement and direct a Star Wars movie again?

RH: Look, I think fans are going to define a lot of it. It's a question of what level of enthusiasm is there for this corner of the galaxy and this set of characters in this time frame.

Coming back to Star Wars? Lucas made his first outing to a Star Wars premiere in years, accompanying his old friend Ron Howard. Image: kevin winter/Getty Images

M: You've also said that George visited the set and contributed to a scene. Did he write any lines?

RH: It wasn't a line. It was an attitude, it was a behavior, it was physical comedy. It was really interesting because when he pitched the idea, he played Han Solo. The scene [involves] one of Lando's cloaks. Alden [Ehrenreich, who plays Han] was taking it and hanging it up. George is like, "you know what Han would do," and he takes this cloak and throws it over his shoulder. For a minute he had the swagger of Han Solo. Which George generally does not carry around with him.

M: You were brought in more than halfway through the process [replacing original directors Phil Lord and Chris Miller, who were fired over creative differences]. Can that kind of creative constriction be a good thing?

RH: I don't think that's ever an ideal circumstance. It was difficult for everyone involved and a shame. But as a creative test, as a moviemaking challenge, it was pretty remarkable and it did force me to rely more on instinct than probably any other project. I needed to rally a group of very talented people and quickly glean from them their ideas. Here are my thoughts, here are my reactions, what are yours?

I was encouraged to make the decisions quickly and get it done. But there was a lot of experimentation, and in that there was a kind of a freedom — let's try this, let's try that, with one goal in mind, which was maximizing the possibility of this great character.

Solo opens everywhere May 25.