- The Danza:
- Jimmi Simpson as James Walton.
- Tom Mulheron as Walton's son Tommy.
- Voice-Only Cameo: Aaron Paul's voice is heard as the gamer who harasses the crew when they manage to break out of Daly's universe.
- What Could Have Been:
- It was originally supposed to be explained how Daly was able to create copies of his coworkers and give them their personalities and memories. It would have involved integrating the grain technology seen in The Entire History of You. Brooker felt that this resulted in too much exposition that hurt the episode's pacing, so it just gets handwaved in the finished product.
- The final shot of the episode was originally going to be the lifeless Daly slumped in his chair as his mind becomes trapped in the game. Brooker felt that this was too dark to end on, so this scene was moved up a bit.
Trivia / Black Mirror: USS Callister