I love this thread. I, too, am an authenticity nerd. (By the way, I consider "nerd" to be the authentic spelling, and I cite "Revenge of the Nerds" as my authoritative source. According to IMDb, there have been 17 movies with "nerd" or "nerds" in the title, but none with "nurd" or "nurds.")

Many years ago, as a college student, I went to see "Lord Jim" with a friend who had grown up in Thailand and India. (His parents were missionaries.) He pointed out several glaring (to him) errors. The plot involves a ship taking a load of Muslim pilgrims from (I think) India to Mecca. He said, "Those [extras] aren't Muslims. They're Sikhs." He could tell by the way they were dressed. In another scene he said, "That's a Cambodian village," where the locale was supposed to be some other country. He recognized the way the houses were built and arranged. It was an enlightening experience.

Anyone who loves movie goofs should love IMDb. You can bring up any movie and then click "goofs." For example, here's their list of goofs for Gettysburg. IMDb does a good job of separating matters of verifiable fact from matters of opinion or artistic judgment. They don't list "not enough blood" as a goof.

Even TV nature documentaries have never been the same since I learned that the sound tracks are usually created by Foley artists. Of course! When the pictures of mating toucans (or whatever) are taken from 100 yards away with telephoto lenses, how else would you ever hear the delicate sound of ruffling feathers?

And on those exploration documentaries, does it ever strike you as odd that when the spelunkers enter the cave for the first time (or the divers enter the sunken wreck, or the mountain climbers arrive at the peak) there is somehow always a camera set up there to capture the moment?

A friend of mine who works in construction hopes PBS will do a special program of "This Old House" outtakes, during pledge week. But I don't think they'll ever do it because it would destroy the illusion that the show is unrehearsed. They do a good job of creating the impression that they're just casually wandering around a construction site and asking spontaneous questions, but how come you never see them make a mistake, even a trivial one? I'd like to see Steve Thomas walk up to somebody and ask, "Say, I understand you're using a new kind of grout on this project, right?" and get the answer, "Who, me? Nah, I'm not the grout guy. I'm just takin' a cigarette break here. The grout guy is over there, takin' a shit."