Two Words: Deep Throat
Another way of thinking about it. There are lots of classic movies out there, and portions, scenes, or dialogue in some those classic movies have become part of pop culture. But the movies themselves, while interesting, aren’t that interesting for the average viewer. So no one really needs to sit through the classic movie “The Birds” to understand pop culture references to “The Birds”. Does anyone really need to sit through “The Omen” just to get the pop culture references to “The Omen”?
Kind of like Don Novella/Guido Sarducci’s college diplomas. You don’t have to learn what people typically learn in college, you just have to learn what people remember 10 years after you’ve graduated. A couple of hours of cramming and you’ll know just as much as a typical graduate does 10 years later.
So I take the OP to mean, “What classic movies are there where all you need to do is watch a couple of minutes of clips and you’re good to go?”
So there’s absolutely no need to watch “Seven Year Itch” unless you like that sort of thing. All you need to do is see the clip of Marilyn Monroe’s dress blowing up. Then you’re done. Nothing else about the movie is particularly memorable. “Soylent Green” is another example, the only thing you need to know about the movie is that Soylent Green is people.
“Casablanca”, “Pulp Fiction”, “Star Wars”, “The Wizard of Oz”, “Citizen Kane” or “Gone With the Wind” are pretty much the exact opposite, they are classic movies that have so saturated pop culture that a boiled-down clip show version of them would be almost half as long as the movie itself.
Lemur866 explained it better than I could :smack:
So we’re looking for unmemorable movies that have one or two scenes that have made it into pop culture?
I nominate “I’ll have what she’s having” and “You had me at hello”. Because the rest of those two movies are pretty unmemorable.
Using Lemur866’s definition, I nominate the Odessa steps sequence in The Battleship Potemkin.
“The Treasure of the Sierra Madre” : All you need to see is the scene where they don’t say “Badges? We don’t need no stinkin’ badges!”
Rosemary’s Baby: He has His Father’s eyes.
Deliverance – You sure got a purdy mouth.
Airplane – and don’t call me Shirley.
Mommie Dearest – No. Wire. Hangers. EVER!
Okay, I get it.
All you need in Psycho is the shower scene. And maybe Anthony Perkins saying, “Mother…?”
Similarly, all you need in Planet of the Apes is Charlton Heston on the beach, saying “Damn you all to hell!” (I won’t say more here–don’t want to ruin it for anybody who has not seen the film.)
And like any Mel Brooks film, Young Frankenstein has a number of things, but you’re pretty well off if you’ve seen the part where Dr. Frankenstein corrects his college class as to the pronunciation of his name, Igor says “Walk this way,” Frankenstein says, “God, what knockers” at the castle door, and the horses whinny each time Nurse Diesel’s name is mentioned.
Have I got the idea?
One more from Casablanca: “Round up the usual suspects”.
I’ve got one!
The Outsiders - “We’ll do it for Johnny!”, and perhaps “Stay gold, Ponyboy.”
Two phrases that pop up quite often in conversation in my group of friends. 
Frau Blucher, Frau Blucher, Frau Blucher, and now I can’t hear for the horses whinnying dammit.
:smack: Yes, you’re right. And would somebody shut those horses up!
Well, you’ve gotta have:
“PUUUUUIIIIN ONA RIIIIIIIIIIIIZ!!!”
In your Young Frankenstein montage.
Young Frankenstein and Casablanca aren’t really good candidates for this treatment. Casablanca is just about the worst candidate for this treatment in all of movie history, because the whole movie is packed with classic lines and scenes, there practically isn’t a single scene that isn’t a classic scene.
Other classic movies, not so much. They’ve got one or two memorable moments, plus a lot of boring unmemorable filler. Y’know, the scenes they show on “Tribute to Hollywood” montages that everyone has seen, but no one really remembers the movies they’re from.
So On the Waterfront: “I coulda been a contenda!” scene counts, even though the rest of the movie is pretty good, because for all the other good scenes in the movie this one stands out head and shoulders over the others.
Rocky:
He runs up the steps. He hits a side of beef. He says “Yo Adrian”. That’s all you need to know.
Jaws: “You’re gonna need a bigger boat!”
Butch Cassidy & The Sundance Kid: the cliff scene and the ending
Easy Rider: “Why don’t you get a haircut?”
That, and a shark’s-eye-view of a shark attacking a young girl while music goes “dun-dun, dun-dun.”
A Trip To The Moon: The Moon gets hit in the eye with a rocketship.
Why do I have to be Mr. Pink?
Because you’re a faggot, that’s why!
Cool Hand Luke
“What we have here is a failure to communicate.” and the egg eating thing.
Poltergeist
“They’re heeere” and “You moved but headstones, but you left the bodies, you son of a bitch”
Don’t forget “This house is clean”, but you have to say it in your itty bitty voice.
Well, the acid-trip-sequence at the end often gets referenced in discussions (both live and in other media), and I’ve seen visual references to some of the special effects elsewhere, too (I’m thinking specifically of the velcro-shod Pan Am stewardess, and the jogging in the centrifuge).
Also the touching-fingers thing that makes the glow. Bonus points if it’s combined with a reference to Michaelangelo’s Creation of Man.
And I agree that Casablanca just has way, way too much to fit into a thread like this. A few hours ago, I told my lab class that I was “shocked, shocked to find errors in the lab manual”, and everyone got the reference.
My nominations: Every single TV sitcom is required by law, by its third season or sooner, to have a Christmas episode based on one of the characters wishing he was never born. Based, of course, on It’s a Wonderful Life. Watch the five minutes immediately before and after George Bailey makes that wish, and you’ll get all those references.
And in Ben Hur, once you’ve got the galley-slave scene, and the final chariot race, you’ve got all the references covered.