Fictional works that are revealed to be fictionally fictional

Oh man, Group 10 is seriously weird. Bewitched and Star Trek?

There was a guy who looked like the Kobayashi he described, but the name was fake—it was from the coffee cup. So for all we know, “Kobayashi” could be a hitman, a driver or his damned boyfriend.
Also, he could check to see if the NYF Taxi Service bust happened, but that doesn’t prove any of the Usual Suspects were involved in it.

The novel The Double Bind by Chris Bojalian somewhat meets this. A lot of what happens in the story turns out to be the delusions of the main character, whose mental health is decompensating. I also found it not terribly effective, but that’s more of a review than you’re asking for.

He could check on the lineup that preceded the Taxi Service heist. And even if “Kobayashi” was just his driver, his appearance lends credence to that part of the story being somewhat accurate.

Are you sure about that? I thought the ending indicated that, after all the to-ing and fro-ing about the script and who was going to have the success with it, Helga ironically ends up with the hit play based on the real events from the rest of the movie.

The last scene of 30 Rock reveals that the entire series was

being pitched to ageless NBC head Kenneth by Liz Lemon’s great-granddaughter, 100 years in the future.

All we know is that Pete Postlethwaite is the face he is thinking about when talking about Kabayashi. We have no idea who he actually is.
It probably falls under the OP’s “It was all a dream” prohibition but I’ll say Brazil. At first glance you think you know what happened but when did it stop being reality and begin being a product of his tortured mind?

About halfway through Gambit, we discover that what we’ve been seeing is Michael Caine’s plan for a heist, not the heist itself.

“L–d!” said my mother, “what is all this story about?” -

“A COCK and a BULL,” said Yorick - “And one of the best of its kind, I ever heard.”

If it’s a bald-faced “this whole this is made up,” as opposed to “this was a dream,” then the work (if published or filmed) would almost by definition be ‘cult’ or otherwise non-mainstream.

I think this is because though we humans admire successful trickery (both because we’d like to have that skill ourselves, and because we don’t want to fall prey to trickery practiced by others), we don’t like to have the obvious shoved in our faces.

And obviously a work of fiction is…a work of fiction. To have the “twist” be the author saying, in effect, “Haha you losers, I made all this up!” doesn’t seem clever to us. It just seems rude.

In a sense, The Matrix. We are presented with the notion that what we think of as the real world is actually a fiction, a computer simulation; and then we are shown the actual real world. By the end of the trilogy, it’s strongly implied that the “actual real world” is also a simulation.

Buffy the Vampire Slayer does this in the episode “Normal Again.”

An Occurrence at Owl Creek Bridge.

See also: Atonement.

Another really good literary example is The Real Life of Alejandro Mayta by Mario Vargas Llosa.

Not at the end of the work, but a later installment in the franchise, but the anime movie Macross: Do You Remember Love? was revealed in later Macross series to have been a movie within the Macross universe.

Mark of the Vampire. The audience is left in the dark as to the actual goings on until the denouement.

Does If On a Winter’s Night a Traveler count? I don’t know, and I hated it too much to think through it.

In Rosenkrantz and Guildenstern are Dead, the characters are somewhat aware that they’re characters in a play, and not real people.

And one of my favorite fan theories is that even the "real"world we see in Zion is actually still the Matrix, due to Cypher’s ability to jack in in the first movie without an operator and Neo’s ability to use Matrix powers in the tunnel vs. the squids.

Which reminds me… Inception qualifies, if you buy into the theory that the entire movie is… whoops, no, it’s just a dream. Carry on.

It’s implied in Seven Psychopaths that the only “real” scene is the conversation between Zachariah and Marty at the end. Everything else is the film that Marty’s been writing, also titled Seven Psychopaths.