While they don't share any scenes together, Michael Bow and Yoshi Sudarso previously appeared together in The Maze Runner (2014). Bow appeared as one of the Gladers, while Sudardo was the stunt double for Ki Hong Lee.
Both Carlin James and Anthony Ma are Shondaland veterans. Carlin was filming How to Get Away with Murder (2014) during the same time he shot his scenes with Dionysio Basco and Chance Calloway, and Anthony did a four episode arc in the fourth season of Scandal (2012). Michael Bow, who plays "Genie" would later make an appearance on HTGAWM as well.
The first season was shot out of chronological order over a period of seven months.
Creator Chance Calloway often writes with actors in mind, and the roles of Ellington, Sunji and Alexander were originally written with Dallas Wade, Charles Melton and Jason S. Mordeno in mind, respectively.