According to the home-release extras, there was more CGI geometry in just one of Alita's eyes than for the entire character of Gollum in 'Lord of the Rings.'
This marks the first professional collaboration between James Cameron and Robert Rodriguez. Due to his prior commitments to direct the four sequels to Avatar (2009), Cameron could only serve as the producer and co-screenwriter on this film, with Rodriguez taking the directorial duties. In an interview with Empire magazine on December 8, 2017, Rodriguez said of the collaboration with Cameron, "This just doesn't happen. Guys like Quentin Tarantino and Jim only write scripts for themselves to direct. When Avatar becomes the biggest movie of all time, he told me that he's going to spend the rest of his career making Avatars, so I said, 'What happens to Battle Angel then?', because as a fan I was just interested! And he said, 'I don't think I'll ever get to do that. Hey, if you can figure out the script, you can shoot it!' So I took it home, spent all summer working on it, cut it down to 130, 125 pages, without cutting anything that he missed. It was a great gift. We had a blast; anytime I had a question I could just call him or email him and he would send back these hugely detailed answers that were so helpful. He just loves being the producer that he always wants. The guy's just so freakin' smart. Getting to learn from someone like that was the greatest internship ever."
The manga series is titled "Battle Angel Alita." In 2010, producer Jon Landau commented, "I'm telling people that we have to call it 'Alita: Battle Angel,' because Jim only does T&A movies." Most of James Cameron's movie titles begin with the letter "A" or "T," Aliens (1986), The Terminator (1984), The Abyss (1989), Avatar (2009), True Lies (1994), and Titanic (1997).
Even though the film is live-action, the main character is done with CG animation and was shot in 3-D, using the stereo imaging system that James Cameron had been developing for his documentaries.
Director Robert Rodriguez based the second Motorball sequence on NASCAR. Instead of aerial and impossible shots, he used the physics of real cameras in placements seen in NASCAR. It includes long lenses capturing things whizzing by, as well as cameras on the track with the players to keep it as "real world" as possible. It was the longest sequence in the film that he worked on, about three years from start to finish.
Robert Rodriguez: [Mexican Culture] Zapan's name is reminiscent of the traditional Mexican almond confection mazapán, and the design on Zapan's back is reminiscent of the Aztec calendar.