Trivia: The name of Truman's boat is the "Santa Maria" - a ship sailed by Christopher Columbus. It is symbolic of going to a new land or a "new" place.
Trivia: The motto on the double archway in the Seahaven town center is UNUS PRO OMNIBUS, OMNES PRO UNO: "One for all, all for one" in Latin, thus fitting the premise of the Truman Show. (00:15:50)
Trivia: A steadfast rule on set was that nobody was permitted to speak phrases from any of Jim Carrey's prior movies. (01:01:45)
Trivia: Visible on Truman and Meryl's kitchen table during an early scene, is a bottle of vitamin D which is needed for all those that do not have proper exposure to the sun.
Trivia: There's a notable difference between the trailer and the final version of the movie. The change was made in the scene where the lamp falls down next to Truman. In the trailer, as Truman looks up, he sees a closing hole in the sky, but in the final version of the movie, this hole is replaced by a lamp post. (00:03:50)
Trivia: Composer Phillip Glass reworked some of his compositions from an earlier film he worked on, Candyman, to fit this film.
Trivia: The scene where Truman draws a picture of himself as an astronaut with a bar of soap was totally ad-libbed by Jim Carrey.
Chosen answer: Clearly, in his media interviews, Truman's best friend, Marion, indicates that he did, indeed, grow up with Truman since they met in elementary school. One could extrapolate that his classmates did, as well. A sudden change of actor from one day to the next would be too much of tip-off to Truman. As actors leave the show, there is a story along with it. His father is presumed to have died, and returns later. I'm sure others move away. The main characters (Truman's wife, parents, close co-workers, and other key figures in his life) also appear to live "in world" and have devoted their entire lives to the Truman project. It is not made clear about the extras, though.
Michael Albert
It's kinda hard to believe though that a little boy (Marion) is faking it all so well for all these years since his childhood without raising any suspicion.
He probably didn't get to know it until a late age. In the bus, a little girl was confused and almost tell her mum that there was Truman, so a kid can't keep up the secret. I'm pretty sure they don't know it. But on the other hand, when he says he wants to be an explorer all the classmates freak out, as if they knew it would put in danger the show. So maybe the classmates and even the best friend had been selected after making sure they wouldn't mess up and reveal the secret.