Yes, well, in keeping with Darjr's reference to Metamorphosis Alpha, I suppose the original official bait-and-switch game was the 1st ed. AD&D module Expedition to the Barrier Peaks, in which the players gradually find out that the dungeon their PCs are crawling in is actually a marooned spaceship. Apparently, as the legend goes, TSR began working on EttBP in 1976, whilst considering publishing a science fantasy role playing game, no doubt spurred by the success of Star Wars, so James M. Ward showed the TSR muckety-mucks his notes for his proposed game Metamorphosis Alpha, and Gary Gygax decided to introduce sci-fi / science fantasy concepts to the D&D fan base via a tournament scenario at 1976's Origins II.
I did play EttBP with my friends in our early gaming days, and I didn't like it because I did feel betrayed by it -- cognitive dissonance set in as outer-space invaded my sword-and-sorcery. Of course, at the time, I was unaware that a lot of Clark Ashton Smith's sword-and-sorcery stories involved Lovecraft's Outer Gods and other such story elements from outer space. Had I known that, I might have been able to digest EttBP a little better.
Later in my gaming years, Cthulhu was omnipresent in almost every setting with supernatural or sci-fi forces my gaming groups and I ever played. But by this time, I understood that a lot of the creatures from the Monster Manual had been rip-offs of Lovecraftian monstrosities, and that by Lovecraft's own mythos, those monstrosities came from space. So it didn't cause me a problem to see a Lovecraftian horror in a sword-and-sorcery game, in a pulp game or in a sci-fi / space fantasy game at all.
In my middling years of gaming, I played a 1930s pulp game (using the Champions system) that was our gaming group's flagship game. We played weekly for over a year, fifty-some episodes, and even had a spin-off "kids' pulp" game in the same setting. In the middle of the campaign, our characters went into space and landed on a world with weird aliens that were space-Nazis. I was able to swallow it, but I didn't like it. Again, it caused a sort of cognitive dissonance, and seemed like mixing genres. But...I understood where the GM was coming from: he was inspired by the pulps of the 40s and 50s that introduced more and more sci-fi elements into pulp. But I couldn't wait for the characters to get back to Earth and for the sci-fi story arc to end.
I did learn a lesson about the "social contract" of the gaming table from a member of that same gaming group when I played Traveller with that group, and decided to play a character inspired by the doctor from Lost in Space. My character was a very competent science officer who was actually a spy, and at a critical point in the first session, he turned on the PCs and stabbed one of them (making him unplayable as a PC for the rest of the campaign). Most of the players thought that was an interesting turn of events...except the player whose character was stabbed. She took me out to dinner and explained to me why that violates the "player social contract." That discussion opened my eyes. I saw the error of my ways, apologized for it, and promised not to do that again unless we all, as players, know ahead of time that such a thing is a possibility. I think Firefly the t.v. series did this well when it made clear that Jayne's loyalties were always with whoever was going to butter his bread the thickest. So, when Mal puts him in that airlock for selling out Simon and River to the Feds, it all seems to work because the audience knows that Jayne is at any time capable of such a thing.
I guess the closest I ever came to baiting and switching -- though it was much more like Umbran's anecdote about the White Wolf game that promised something more -- was also a WOD game, a Wraith game I ran with a single player that tried to capture that Sixth Sense moment where the PC would suddenly realize he was dead, and a ghost. I told the player we were going to play a game where we generated his character as we played, and didn't tell him what system we were using. I had gamed with this player since my earliest days of gaming, so we trusted each other and I knew his tastes very well. I had his blank character sheet behind the shield, and I would ask him in situations HOW he would resolve them, statting the character out for him behind the shield based on the information he fed me.
Midway through the first session, though, as I was flipping through the book, the illuminated pages of the Wraith book peeked up over the shield, and he saw. "Oh! We're playing Wraith!" he said. The surprise was blown. But we carried on anyway, and had a good game nevertheless.
