There was one thing Angela Lansbury wouldn't do for Glass Onion: learn to play Among Us.

Innersloth's 2018 phenomenon "Among Us", for the uninitiated, is an online mystery that is played in groups. Players, each playing from their own computer, are assigned an identity at the start of the game. Most players are astronauts in shiny uniforms - crew members - who must run around a spaceship performing very simple tasks to prevent the ship from malfunctioning. Some players, however, are secretly disguised aliens - impostors - who attempt to kill crew members undetected. If suspicion is high, players can call meetings and vote to get other players to vote. Those who have been rejected will be thrown into the void of space, whether they are imposters or not. If the Imposters are detected, the Crewmates win. If the teammates are all killed, the Imposters win. This is an interactive version of similar elimination games such as "Mafia", "Cry_Wolf", "Werewolves Within" and "Bodies Bodies Bodies".

Benoit Blanc, according to his screen preview in "Glass Onion", was an impostor named BlancMan22 whom Stephen Sondheim, Angela Lansbury, Natasha Lyonne and Kareem Abdul-Jabbar detected and dumped from the ship.

According to a December 2022 interview with The New York Times, Rian Johnson said he always wanted to work with both Lansbury and Sondheim because he, along with much of the planet, was a big fan of their work. Additionally, both performers were known, at least in part, for their involvement in the murder mystery media itself. Lansbury appeared in the long-running television series "Murder, She Wrote" and Sondheim wrote the 1973 Robert Hoss murder mystery film "The Last of Sheila" as well as the short-lived stage play "Getting Away with Murder." in 1966...they were clearly thriller fans, and it stands to reason they could, in real life, be friends with an eccentric P.I. like Benoit Blanc.