1.The large black "diamond" on Truman's ring is a camera.
2.Truman is shown to have Vitamin D pills — a supplement that's utilized by people who don't get enough sunlight.
3.The text on some arches behind Truman in one scene reads, "Unus pro omnibus, omnes pro uno," a Latin phrase that means "One for all, all for one."
4.It's stated that the show makes money using product placement — one example of this is when Marlon made it a point to showcase the beer he was drinking.
5.When Truman unexpectedly decides to leave his office, he enters and immediately exits a revolving door. This throws the camera operator off, and you can see them unsteadily scrambling to get a shot of Truman from a distant camera.
6.When Truman is telling Marlon he thinks strange things are happening, Marlon is pretending to work, stocking a vending machine. When Truman turns away, Marlon removes some candy bars, before restocking them while continuing the conversation.
7.In one scene, a "street cleaner" can be seen pretending to pick up trash and put it in his bag.
8.There are cameras subtly placed throughout scenes, like this one on the neighbor's trash can.
9.At one point Marlon comments on a beautiful sunset that's actually fake, but Truman can't tell because he's never seen a real one.
10.When Truman is starting to figure things out, the control room director can be seen skimming the classified section, presumably looking for new jobs.
11.When Truman goes to meet a travel agent, she shows up late and is wearing a napkin/bib, presumably from being hurried through makeup or rushing over from lunch because her character hasn't been needed before, as Truman's never traveled.
12.The boat Truman rides as he attempts to venture out is called the Santa Maria — the name of the largest ship Christopher Columbus used on his first voyage.