The Thing. Specifically when the severed head sprouts spider legs. It still sends shivers down my spine.
You don’t say but I assume you’re thinking of the opera debut scene in Citizen Kane. The DVD copy I have of that movie includes a commentary track by Roger Ebert in which he describes the special effects in the movie. I think he even called it the Star Wars of its day. There was one scene, for example, where the camera starts outside a small cabin in the woods, and moves forward into the cabin. I think he said the effect was accomplished by pulling the two halves of the cabin apart.
It was the Australian censors, and I have it backwards-they insisted that to keep a rating for children, the monster should NOT be seen. Thanks for fighting theatrical ignorance!
TFP was shown on a local educational TV channel many years ago, and that’s where I got my backwards info. The local TV guy did interview Leslie Neilson about among other things the Star Trek similarity.
See “alternate versions” in the IMDB article.
The question remains, “Why was the Id monster made visible?”
I feel like I just learned Santa Claus wasn’t real. 
I’ve always liked the giant squid attack from 20,000 Leagues Under The Sea.
Wait, what?
Although I’m sure it wasn’t as challenging as Kermit riding the bike, Fozzie driving his Studebaker also took some doing. They had a human driver in the trunk driving the car by remote control, watching the road through a camera concealed in the front of the car. Meanwhile the puppeteers were lying down on the floor of the car operating the Muppet characters to make it appear Fozzie was driving. And ever since I learned how they did it, I figured that was the reason they picked a “bullet nose” Studebaker as Fozzie’s car – the car’s nose made a perfect spot to hide the camera for the remote driver.
Labyrinth is famous for the CGI owl, but most of the effects were done in camera. Jim Henson was not happy with some of the puppetry, but that was still some of the best puppet-work ever done.
But my personal favorite is when the goblin-king juggles the crystal balls. This video shows how it was done: Labyrinth - Contact Juggling / Sphereplay - YouTube
I had the DVD with that commentary track - I think Ebert was talking about this shot, where the camera pushes through a sign and into a skylight. The sign was designed to pull apart once the lens was close enough that you couldn’t see the sign any more, to let the bulk of the camera pass through. If you look closely, you can see where the bars holding up the letters are cut in the middle, right underneath where the camera passes.
Of course, they might also have done a similar thing with a cabin.
I’ll have to watch that again, but my recollection is that it didn’t look at all like a movie – I thought Reeve was interacting with Kidder before he takes off.
I don’t trust IMDb 's explanations for how effects were done. IIRC, they were among those who claimed there was a cutaway between the card tricks and the shot of Newman’s face in The Sting,. They also claimed that the parting of the Red Sea in the original , silent [i[Ten Commandments* was done by heating the “walls” of the sea (made of gelatin) with a heat gun until they melted, then running the scene backwards. Having watched the scene numerous times, I find that explanation laughably incorrect.
Another Buster Keaton one is the waterfall scene in Our Hospitality. It is more of a stunt than special effects.
The Mutara nebula in Star Trek 2 The Wrath of Khan was achieved by filling a tank with a mix of fresh and salt water with a barrier between them and then removing the barrier and illuminating the setup with colored lights.
Nowadays, I suspect, it would all be done with CGI and wouldn’t look as good.
I always get a good chuckle out of old movies that have scenes of a ship on a lake or ocean because they’re so comically and clearly toy boats on a fake body of water.
Here’s the scene. Now that I read how it’s done, it’s easier to see. He interacts with Lois, then in the last cut, turns away and takes off. He definitely looks a little “flat” and washed out in that final cut.
I was given to understand that they built dams, opened them, and showed the film in reverse.
I grew up, like many, thinking Lloyd did that stunt at his own personal risk.
Did Buster Keaton do this insane(illegal?) stunt sequence on a motorcycle?
Just for historical completeness, in case anyone here hasn’t seen it yet, we have Dream of a Rarebit Fiend, 1906. Utterly primitive (by any imaginable modern-ish standard) film full of early “trick photography” (as I suppose it was then called). 7 minutes long. Soundtrack apparently added more recently – there are several copies of this film on YouTube, apparently all with different sound tracks.
Synopsis: Man pigs out on Welsh Rarebit (a fondue sort of dish) and wine, gets drunk and sick, stumbles his way home, crawls into bed, has headache and bad dream.
(Note: YouTube title line says 1903, but that’s apparently wrong. The title shot in the film says 1906 in the lower right corner, as well as all the other YouTube pages with this film.)
Hell, “Star Wars” is 42 years old now. So, that.
The ‘Tingler’ with Vincent Price. I didn’t sleep for a week after that scary thing.