Not true. I posted an answer in the original thread along the same lines as one_madJack’s. I suggested “Moonstruck” as the other movie since it also won Best Actress and Best Supporting Actress. I was wrong, since other movies have won both awards, but it was a try.
You say there’s only one existing movie that fits the category. Could another movie ever be made with the same characteristic, or are these four the only ones there will ever be?
You’re right. I apologize for the hyperbole (I did remember your guess), but yours was at the beginning of the post, whereafter the question got quickly buried/passed about.
No, read my OP in this thread–it doesn’t have to do with some trivia regarding the ceremony. To clarify, the answer lies in the Academy’s roster of Oscar winners. (How’s that for another hint?)
You are definitely on the right track. Here’s another hint: John Ford
No
Yes
Yes, but (he said cryptically) you haven’t gone far enough…
Actually, a little of both–the answer is directly related to the Oscars, but knowing that is also a huge hint since the fourth has an Oscar connection without being nominated itself.
No, although you make a slight misstatement about Streetcar which is actually pretty important. As for your last guess, No, this is something very specific and factual, not vague and amorphous.
There is always the possibility that additional films will join this list.
Wow! You are definitely making headway. If I had to choose one film of the three as a real lynchpin to the answer, it would be GWTW. Good Luck.
Another stab, but I’m not sure how it relates. I think that John Ford may have one one of these. And yes, I know what Cinerama is, smartass! 
Quasi
I looked at that, but couldn’t come up with any tie-ins yet. Still trying…
Not sure how that would relate back to the Academy Awards, though.
Paul
Sorry, I was referring to AFI’s Lifetime Achievement Award. John Ford was the first recipient, Barbra Streisand the most recent. A complete list of winners by year can be found here.
I think I have the film, but I don’t yet know for sure why…Which means I’m probably wrong.
Paul
Yes, I misstated which film has the most acting awards. Actually, Streetcar and Network share the record for most acting awards: Streetcar won Best Actress, Best Supporting Actress and Best Supporting Actor (Karl Malden). Network won Best actor (Peter Finch), Best Actress and Best Supporting Actress.
John Ford has won the most awards for directing: (The Informer (1935), Stagecoach (1939), How Green Was My Valley (1941) and The Quiet Man (1952)).
I’m still trying to find the similarities, but until I do, I thought I’d just take a wild guess and say:
The Mosquito Coast
It wasn’t nominated and the director (Peter Weir) is not American.
Okay, here’s another guess, but I hope it’s a little closer to fitting the requirements:
** The Manhattan Project**
It boasts a cast member Bran Ferren who was nominated for an Oscar (not for his performance but for visual effects–for Little Shop of Horrors) who lost, only to win two additional Oscars (Techinical Achievement Oscar for the development of a laser synchro-cue system for applications in the motion picture industry and a Science and Engineering Oscar for the concept and design of an advanced optical printer.)
Heck, maybe he’s the only person to win both a Science and Engineering Award and a Technical Achievement Award. Haven’t had a chance to look that up yet.
I still don’t know if any of this counts or if the link to the Manhattan project is valid, but I thought I’d put it out there. The Manhattan Project was not nominated and its director, Marshall Brickman, is from Brazil.
Oops! That’s not correct. Ford didn’t win for Stagecoach. Can’t remember where I found that info, but it’s clearly wrong. Amend the above answer to include The Grapes of Wrath (1940) in the place of Stagecoach.
(please, please let this be the last correction I have to make!)
They all contained actresses who have never been in my kitchen?
Thank you! I’ve been waiting a long time to see someone state this! 
This is a really tough trivia question. I’ve been trying to find the answer, and just can’t seem to pinpoint it.
Does it have anything to do with Peter Finch being awarded his Oscar postumously?
No, though Finch’s win itself does play an important part.
Whoosh! What was that sound? It was an enormous hint that you yourself brought up in this post and then subsequently dropped! Go get it!
As for Manhattan Project and Mosquito Coast–forget them. This doesn’t involve some obscure nobody. Think John Ford (heck, think John Wayne too) + GWTW = ?
No offense intended, but these you never know.
I meant these days, you can’t be too sure.
I’m thinking Top Gun, but for the life of me I don’t know why.
Except that it was the top grossing film of '86, and Tom Cruise’s next film was The Color of Money in which Paul Newman won his first Oscar.
???
Does it have anything to do with previous or subsequent films? Like the director’s previous film was something special (e.g. Victor Fleming’s Wizard of Oz right before he did The Wind Done Gone)?
Top Gun won an oscar for Best Song, however.
I’m pretty sure this has to do with movies that have had actresses and/or actors that hold the Best Acting and Best Supporting titles respectively.
Since I have not seen any of the movies, I have no idea what this connection would be. However, it seems obvious that the fact that the three movies mentioned all won the two best acting awards for the same sex has something to do with it.
I’ll take a double stab at it:
It’s the only other movie that has featured best actress and best supporting actress (Seems like this must have happened before and since, though)
It’s the only other movie that features best acting AND supporting acting for BOTH sexes. Now, I have no idea if the other three won this award, so this is kind of a wild guess
I doubt my logic is enough to beat this one, but I’m just as annoyed by not knowing the answer as those of you that have seen the flicks 
— G. Raven
Umm…is this a movie that “John Q. Public” would know?
(Sure, it may be the only one with something in common with the rest, but if no one has heard of it, there’s no point…just curious…)
I still don’t know what the common link is, but a movie that I think fits most of the hints is Aliens.
But it has Oscar nominations and won for best visual and sound effect.
Thanks, Archive Guy, for all of your help. I know it must seem obvious to you, but I’m still struggling a bit.
Okay, here goes:
Heartburn
It stars the actor and actress with the most Academy Award nominations.
If this is not the answer, I also have some half-baked theory regarding an uncredited writer from GWTW and Stagecoach. Guess we’ll see.
MJ