Visible crew/equipment: During the shooting, a crew member holding a camera is visible in the upper right side of the screen. (00:22:39)
The Man with the Umbrella - S1-E3
Continuity mistake: When people start dying during the dalgona game and people start getting eliminated from the floor of the control room, you can see one of the screens on the left showing a player licking the back of his cookie. People don't start doing this until they see Gi-hun come up with it, and he hasn't had that epiphany yet. (00:39:26)
Trivia: They keep guessing the next game, however clues are hiding in plain sight. The illustrations on the dormitory walls depict all the games, from "Red Light, Green Light" to the final match of Squid Game.