To prepare for the show, many of the actors received different forms of Halo media to study. Pablo Schreiber, who plays the Master Chief, watched every Halo cutscene from the games, watched every live action movie and animated short, as well as read several of the books and graphic novels. Kate Kennedy, who plays Kai-125, beat the campaign for each main Halo game and read The Fall of Reach. This comes from Schreiber and Kennedy's interview with Paramount+.
Natascha McElhone was originally set to voice Cortana, until Jen Taylor, who voices the character in the Halo video game series, replaced her. McElhone plays the role of Dr. Halsey only.
Pablo Schreiber said his Master Chief armor weighed 50 pounds. Bentley Kalu reported that his armor for Vannak-134 weighted roughly 30 kilograms (66 pounds). In the main Halo canon, the Mjolnir battlesuit weighs 1,000 pounds when in use.
Actors Pablo Schreiber, Natasha Culzac, Bentley Kalu, and Kate Kennedy (who play the Master Chief, Riz-028, Vannak-134, and Kai-125) underwent a week-long military boot camp in Budapest, Hungary. They were drilled on squad formations, military etiquette, equipment, weapons training, teamwork, physical training, patrolling, and how to react under enemy fire.
Filmed in Hungary, mostly in Korda Studios in Etyek, near Budapest.