The Truman Show/WMG

Truman will return to the show
After living for his entire life in a carefully conditioned environment, he won't be able to handle the real world, or more specifically, the celebrity status he will get from it. He has no real abilities to speak of; they presumably didn't challenge him in school because they wanted him to pass. Even assuming he meets up with Sylvia and that she helps him out, he'll eventually have a breakdown and return to the show.
 * And then what? Sailing off was the point of no return to him. Even if Christof managed to convince him to return, the show would never be the same with him clued in that he's living in a fake world.
 * Similar to Real Life cases of PTSD - many people just wish they could go back to "the way it all was before"... but they have to deal with the reality and find peace with it (after a lot of grieving).
 * Note also that the appeal of the show for audiences was that it was a 'real life' -- the fact that Truman didn't know what was going on meant it was unscripted and genuine, which is where a lot of the appeal came from. If Truman comes back knowing full well what the score is, that appeal is completely lost; the new show would probably haemorrage viewers since it'd be no different to anything else that was on.

Dog Fancy contains real world news, rather than the fake news that the Island would always receive in its paper - which Truman would pick up.

 * One would have to wonder how they'd avoid letting Truman buy it, then, if he suddenly decided to try it out--because everyone else was reading it!
 * It would be a specially-made edition, of course, provided by the publishers as part of the product placement. It would look pretty much like the real-world version, but censored as required by Christof.
 * I daresay the cashier would be able to pick Truman out of a crowd and give him a copy of Dog Fancy with puppies in it.
 * Plus, the show's staff could warn him in some way that Truman is getting close to his shop.
 * And they made it clear that Truman had a fear of dogs, in addition to the sea. His aversion to dogs would make the dog magazine the best place to conceal real news, since its the magazine that he's most likely to avoid buying.

The Truman Show (the show itsself, not the movie), is trying to attract a Periphery Demographic of Yaoi Fangirls.

 * Because Marlon and Truman seem to have a sizeable amount of Ho Yay.

The show is being filmed inside a Geofront from Evangelion.

 * If you think about it, even the landscape is similar to the Geofront from Evangelion, even the lake is there!

The film states that Truman is the first child to be adopted by a corporation. Does this mean that there are other "shows"?

 * The film says that it's the first one of it's kind, suggests that it's the biggest and most popular, but that doesn't mean that it's the only one, just like the Big Brother TV series IRL.
 * Truman was also the first-born of the five unwanted pregancies. It's possible that the other babies were adopted, too, as they didn't know at the time which baby was going be born on cue and wind up as the subject of the documentary. After it became apparant that they were going to use Truman, the other babies were given up for adoption.
 * No, of course not. Don't be ridiculous. It just means that he's the first child so far to be adopted by a corporation. Just like Barack Obama is the "first black President".

Truman has always noticed something wasn't right about his hometown and its people.

 * While it true that Truman has never known anything but this fake reality, it still doesn't change the fact that because everyone around him are actors, he might be subconciously noticed that they are fake, but as he has no reference to compare it to, he wasn't able to put his finger on what it is until the accidential mixup with the car radio.
 * Given the scope of the project, it's also probable that instead of the radio mixup suddenly blowing their cover in year 30, little errors like that have been occurring here and there throughout Truman's entire life. The producers were usually able to smooth them over(as we see with the broadcast about the airplane shedding parts after the Sirius light falls, and Truman's subsequent putting it out of mind), but eventually, a few of these events happen to occur in such a short time. The mixed-up broadcast alone may not have set him off, but the broadcast, plus the falling light, the targeted rain, etc, and all during a point when Truman is already in an antsy state of mind. Finally, something clicked.
 * This wrongness about his town might very well have only fueled his desire to leave the island town in the form of wanting to explore the world even before he fell for Sylvia.
 * In a way, Truman is like Neo in that they both have always felt something off about the world that they live in, except that he doesn't have a red pill to help him see the truth, he had to discover it for himself.

Truman has never heard a swear word

 * .... or at least one more severe than "darn" or "heck". The Truman Show is clearly meant to be all-ages programming with a specifically clean, wholesome environment. Discouraging swearing amongst the cast wouldn't be enough, as there'd be nothing to stop Truman himself from letting some fly if he were really angry or frustrated, and since it airs live, they couldn't bleep them. The only way around this would be to explicitly forbid the use of any swear words on the set, perhaps by having the actors trained to reflexively say cleaner ones like "darn" or "heck" in moments where you almost have to swear. Ultimately, Truman can't say the f-word on air because he literally doesn't know it.
 * He asks Meryl "What the hell are you talking about?", so he at least knows that one. But still.
 * Marlon also tells Truman earlier "You look like s***" when he visits him at the store. And I believe there's a few "Oh my God"s sprinkled around there.
 * And Christof talks about his dream of filming "the first televised conception of a human being" or somesuch. So it's not exactly "all-ages programming".
 * They cut sex scenes out, as said by one of the viewers, so I'm not sure what Christof meant by this.
 * You probably don't need the sex scene itself. Conception is an internal process; get the right kind of cameras in place inside of Meryl, if you know what I mean (and remember that Christof made his name filming Truman before birth, so he presumably has some experience with filming internal biological processes, such as you might see on a medical documentary), you can show the baby being conceived without having to show the sex act in graphic detail itself. While the sex scenes themselves are cut out (no doubt to appease the censors), they're still presumably filmed, both externally and internally. It looks like Meryl's about to conceive, cut from the wafting curtains or whatever to a live shot of a spermatozoa penetrating an ovum -- bingo, conception has been televised, and the Moral Guardians don't even have anything to complain about.

Other children in Truman's classes were kept out of the loop while on the show

 * Keeping dozens of individual children from spilling a secret that big to one of their friends/classmates would be extremely tricky. An easier way would be to offer parents the opportunity to give their children first-class education in Seahaven for a few years, on the condition that they don't tell the kid about the show aspect until they've graduated, finished that year, etc, at which point they'd have moved out of town or changed classes. Close friends like Marlon would be special projects, requiring intense attention and conditioning not to spill the beans.
 * This fits in with a subtle line of dialogue that implies that Marlon has travelled the world. He may have been Put On a Bus after elementary school, shown the true nature of the show, and then sent back to reclaim his position as Truman's best friend. However, a teenager (since he was shown in high school) would be highly unlikely to willingly go into a show where his friend was imprisoned. On the one hand, they may have used the only actor from Truman's childhood days willing to return to the show to become his lifelong friend, or they may have simply recast the character when his Bus Came Back.

The teacher on the show was extremely stressed out.
Think about it - every educator in the world is watching you - every single class - and evaluating your teaching style.
 * But they're not really teachers; they're actors. Cristof probably fed the teachers lines and gave them a script to follow, and any educators in the real world would realize that they're not really teaching meaningfully. I mean, if you see a teacher on a tv show, you don't evaluate their teaching ability (unless it's a plot point or something) because you know they're acting, so it's the same for this.

Some people worshiped Truman.
Heck, a fair chunk of the world economy must have been supporting the guy. Maybe this is yet another reason Christof wanted to keep Truman out of the loop.

That studio light that fell down from the sky was someone trying to kill Truman.
Out of all the lights that could've fallen it was this one that fell so close to him. Someone was trying to wipe him out to free him from his prison.
 * Or to make him wonder. If someone up there didn't have a spare light, there would be no Dogstar...even though there was one last night.
 * And the spotlight that falls is Sirius - the Dog Star - when Truman is afraid of dogs! Funny, eh?

The biggest group trying to free Truman was the Actor's Union.
Truman has been acting 24/7 for roughly 30 years, and hasn't been paid a dime for it. This was even true when he was a minor. This makes The Truman Show a violation of all union regulations regarding salaries, working hours, and working conditions for a member of the actor's union (Especially the rules about child actors). The fact that Truman isn't a member of the union (Due to the fact that Christof won't let them approach him, because that would cause Truman to learn that he is an actor) makes things worse in their eyes. A major television program is running starring a non-union actor, who is cheerfully working in conditions that no union member would tolerate due to the director controlling said actor's life to ensure that he never learns that he shouldn't be working under such conditions. This is something the union can't allow to stand - if they do, they weaken their position when negotiating the salaries and working conditions for every actor who is a member of the union.

The dome was re-purposed to film The Walking Dead TV series.
Mostly because of Noah Emmerich's (Marlon) bit part at the end of the first season of that show. full details are laid out on that show's WMG page.

When Truman left the show, the economy suffered DRAMATICALLY.
Think for a bit about the sheer number of people involved in the Truman Show. All the actors and production crew (cameras, sound, lights, writers, music, traffic, maintenance, weather, makeup, costumes, set design, crowd control, etc.) would be out of jobs. There would now be a giant area of unused coast land that would either become a tourist attraction, or need to be re-purposed to make actual living possible (most of the buildings and homes are probably just glorified boxes with no real inner workings, in order to save money. Remember the back-less elevator?). Not to mention all the investors that had stock in the show. The entire show was run by in-universe advertisement, and if the show is as successful as it says it is, those companies would suffer HUGE drops in stock. The corporation heading the show would probably have to shut down or declare bankruptcy. If the Truman Show was a significant enough part of the economy, there might be riots to bring it back (or just riots in the face of the crumpled economy. It doesn't sound far-fetched, haha.) This could lead Truman to be a notoriously disliked member of society, and have very few places to turn other than to Christof himself, at which point he may need to live with for a long time until the economy recovers.
 * He obviously wouldn't have to live with Christof given the scores of people who'd devoted their lives to trying to free him from the show who would glady take him in, including, obviously, the love of his life, as well as the fact that he could immediately make millions of dollars just by doing an official interview or writing a book.

Christof died of a heart attack right after Truman left.
It took me a few viewings to notice it, but right after the transmission is cut for the final time, Christof slumped over on his screen. He at least passed out to some degree, but seeing your life's work walk away and leave you forever is surely enough of a sudden stress to kill you.

The dome is actually within another dome.
This way, the show's premise can be recycled with the other actors, who were "waiting" - just like Christof himself - for Truman to eventually snap and get out of there, ready to welcome him as "the real people from the real outside world"... and Christof planned all of this in advance, just in case. Additionally, if this fails, there wouldn't be third dome simply because Christof would be happy with having irreversibly ruined Truman's ability to trust other people, with the second dome inevitably making him even more paranoid. Of course, this theory isn't just this troper being a dick for the sake of it; it is instead a possibility. A grim one, at that, but still a possibility.

Truman will wind up owning Christof's studio.
Christof owes him thirty years' overtime and residuals, which the director had never made allowances for paying off. Between that and the monster civil rights lawsuit Truman has grounds to file against him -- a case Christof won't have a chance in hell to win, after he'd broadcast his own attempted murder of Truman to the entire planet -- the ex-director will have no choice but to forfeit every cent he owns to the one he's been exploiting.