The lead role of Mae was first offered to Alicia Vikander, which according to her, was one of three roles offered simultaneously, alongside the roles of Maria in Assassin's Creed (2016) and Heather in Jason Bourne (2016). Due to fan factor, she opted to do Bourne, thus the producers moving on to casting second choice Emma Watson.
When Mae is getting a tour of the campus facilities by Annie, she is told of the various clubs in one outside area. One of the activities pointed out by Annie was "Quidditch". Of course, the flying broomstick sport of Quidditch was made famous in the Harry Potter universe, in which Emma Watson starred. A land based version of the "sport" has since become popular among university students and tech nerds such as those in The Circle (2017).
While The Circle's campus is computer generated when shown from a distance, many of the outdoor scenes were filmed at or around the Bandshell at Playa Vista Central Park. That area was once part of the Hughes Aircraft complex and still includes some of the original buildings.
During the first speech that Tom Hanks' character gives, he reveals the name of the cameras are called SeeChange. Immediately following this scene they cut to a concert featuring the singer Beck. One of Beck's most famous albums is called Sea Change.
At the beginning of the movie Mae's ringtone plays "Simple Gifts". The mid-1800s Quaker song lyrics start, "'Tis the gift to be simple, 'tis the gift to be free." Toward the end of the movie her ringtone has changed to a simple chime.
At one point Mae struggles to keep up with Annie and comments how incredibly long her legs are. Karen Gillan played Amy Pond on Doctor Who (2005), and at one point another character Clara commented that she, "...is made of legs, that's the most legs on any living human!"
The trivia items below may give away important plot points.
The ending was changed significantly for the film adaptation. In the novel, Mae, fully believing in The Circle's goals and mantras, betrays Ty in his attempt to bring down the company and he is effectively silenced.
In the boardroom meeting, the idea of mandatory voting is brought up. In the former Soviet Union, voting was mandatory and candidates for offices were pre-selected on the ballot by the local Communist Party (one candidate per office). Most candidates received almost 100% of the vote as a result.
When Mae is going transparent, there are many messages from people all over the world in different languages. One of the messages is in Hebrew, and says: "What channel do I need to be on to see some sex!?".