Every performer the series billed in its cast list across its four seasons, from 2016 to 2020 on NBC. That is the whole rule, and it takes in six actors, from the top of the cast list to the bottom of it. The large recurring and guest company is out, however well you remember them, however many episodes they turned up in. One of these actors played several versions of the same character over the run, and the set still asks for the actor once: one name, one answer, however many versions the show gave them. The answer is always the actor, never the character. A surname on its own counts. Nothing in this set gives away the story: no question, clue, option or answer tells you where the story goes after the opening episodes, or how it ends.