Truman's Ford Taurus is actually three different models. The GL, the LX and the performance edition SHO. The models change frequently in the film. The wheels, interior trim, and exterior styling all have subtle (but noticeable) differences.
When Meryl gets in the car with Truman and he drives off to the traffic circle, the above shot shows Meryl wearing her seat belt. A few seconds later as they are driving around the circle, the camera shot from within the car shows Meryl putting her seat belt on.
Shortly after the movie has started we see a spotlight falling down from the sky. When it is about to hit the ground the landing point is in the shadow of a nearby house. Then for exactly one scene right when the spotlight touches the ground and gets destroyed it happens in full sunlight. FInally when it's all over the now destroyed lamp is in the shadow again.
When it begins to rain on Truman on the beach, the single spray head follows him as he runs around. It would take at least 8 or 10 seconds for the rain to reach Truman, assuming the shower heads were up in the sky far enough to not be visible. The shower heads follow him too quickly and appear to be only a few feet above the view of the camera
During his first encounter with the Dalmatian, Truman
shields himself with his briefcase. However, as the angle changes, his case is down by his side, yet the dog is still in position, jumping up.
When the bus breaks down smoke is shown coming from the front. Buses have engines and transmissions in the rear. That's where the smoke should be.
When Marlon is restocking the candy bars in one of the vending machines, he works on filling up one of the rows. The scene switches to Truman talking with Marlon, and when the scene switches back to the vending machine, the row that Marlon had filled in is empty. However, earlier in that scene Marlon can be seen removing two candy bars when Truman is not looking, then stocking them back into the machine. It is obvious Marlon is just acting busy by moving candy bars back and forth, thus killing time and keeping Truman stationary so the important discussion can unfold on camera.
It's quite imaginable that the yacht's sails and lines are in perfect condition, even after 20 years. Story says that Truman developed strong fear of water when his father drowned. In the real world the boat might therefore stay abandoned and not maintained since that event. But in the controlled environment of the Truman Show it is likely that all equipment is maintained to working order. One never knows when the scenario might call for the boat to sail again. Therefore even all thee on board cameras function as required.
An 8-ball that appears to be on Truman's desk (and then disappears) is in fact in a basket on a cart.
Truman's aquaphobia vanishes completely when he escapes from Seahaven on the sailboat. This is logical and rational, since his dead father (the source of his aquaphobia) is revealed to be alive and Truman has realized that the entire event was faked to begin with.
The shape of the moon is not correct during the sunset scene with Marlon and Truman. With the moon that close to the sun it should be a very small crescent but it is shown as nearly full. But any such "goof" made within the context of "The Truman Show" TV show was deliberately added by the filmmakers, and consequently should not count as a mistake in the film.
When Christof touches the huge screen with the image of Truman sleeping, his hand casts a shadow. The control room is not sufficiently lit to cast a shadow. The huge screen, acting as a light source, would cancel out the shadow. This reveals that the scene was composited using a blue screen.
In the cabin camera POV shots of Truman sailing the yacht, if you look at the water you can tell the boat isn't moving.
When Truman is leaving on the boat, a shot of the front of the boat is visible @1.22.15. This is just before they hit him with the storm. The blue screen has been left in and not edited out to show the sky.
The diorama model of Seahaven in Kristof's control room does not represent the real Seahaven, being oval shaped. Yet, the "structure visible from space" is round. Additionally, the diorama clearly indicates no railroads or airports, and the main square is also not represented. There are also much fewer houses in the model than in the real Seahaven.
During the final scene, when Truman speaks to Christof, the open door behind Truman leads to a dark interior. However, during Truman's close-ups, this is clearly replaces by a solid black wall.
In the flashback scene to when Lauren/Sylvia and Truman leave the library and go to the beach, there are no cameras which is presumably why they go there in the first place. The only camera shown to be positioned there that is in the show, is the one on top of the sand dune. However it is revealed that the people in the bar are watching the event too, but it's not explained how they are watching it too, considering that the only time a camera is introduced is when "Lauren's father" drives out onto the beach, at which point basically everything has already happened. Additionally the fact that the woman at the bar requests to see the greatest hits tape, which the scene is apparently on, insinuates that she wanted to re-watch the kiss between Truman and Lauren/Sylvia, but again there is no way they could have seen this because there was no cameras.
When Meryl does her commercial for Mococoa, the label says NO SUGAR ADDED, and she says "All natural, no artificial sweeteners." Sugar is, in fact, a natural sweetener, so a cocoa beverage with no sweeteners would be absolutely undrinkable.
Truman does not find it suspicious that Seahaven has no airplanes and no airports, being a sealed dome, although very large, he could not possibly fly to Fiji from Seahaven. He would have to be on the outside after realizing where he really was.
When the neighbors are walking arm and arm in search lines, the audio is of footsteps marching in perfect synchronization. However, the people's heads are bobbing up and down out of synchronization, and when their feet are shown, they are walking out of step.
The 'set' is supposed to be right behind the Hollywood sign/hills, but in the satellite view, the set is in the southeast LA region, 20 miles from the Hollywood sign.
When Truman disappeared, all crew is called to looking for him. Actors sweeping every inch of Seaheaven side by side, production staff looking "busy" in control room. But that everything is unnecessary, because when Christof realize that "we do not watch water", Truman is very quickly found on boat cameras. So it would be enough to check all camera outputs on first place to find him within few minutes.
Also it's really strange that yacht sails and lines are in perfect condition. Story says that Truman developed strong aquaphobia when his father drowned. Therefore boat would stay abandoned and not maintained since that event. Is not much likely that Truman or anyone else would take care of yacht. However, when Truman going to escape, after approx. 20 years all sails and lines are in perfect condition.
It is an enduring myth that the Great Wall of China is the only man-made object visible from space. The wall is narrower than the average highway and is visible only in low orbit from where all manner of other man-made objects can also be seen.
When Truman notices Meryl's crossing her fingers in the wedding photo, the hand that is visible would be her right hand as she is standing on the right side of the photo looking at Truman who is on the left. The mistake is that Meryl's wedding ring is on the hand with the crossed fingers, which would be her right hand. (This may agree with the "lie" of the crossed fingers.)
There are various people shown watching the show, one of them is a man who spends the entire film in his bathtub, at one point he leans forward to turn up the TV, however he merely twists his fingers on the surface of the tub near the TV indicating that he was pretending to turn it up but he was nowhere near the volume knob.
Truman states that Fiji is exactly on the other side of the Earth from Seahaven. ("You can't get any further away before you start coming back."). In fact, the furthest point from Seahaven on the earth is in the Indian ocean, about 2000 miles off the coast of Madagascar.