For me, it was quite the opposite - when I saw Casablanca for the first time, I remembered all the scenes from it being parodied or quoted, and I thought, "so that is where those came from".
The same happened to me watching The Wizard of Oz. Suddenly I remembered all those scenes from the Simpsons which I did not get before and was like, "now I get it".
There is an episode of Star Trek DS9 where a character almost literally quotes the speech at the end of The Third Man (given, incidentally, by Orson Welles). Had I not seen The Third Man, I would have thought it was just a stupid monologue, but knowing where it came from changed the tone and gravity of that scene completely.
Borges has a story for that ;-)
http://en.wikipedia.org/wiki/Pierre_Menard,_Author_of_the_Qu... - where a book now being rewritten identically word for word is, of course, a completely different book ...
By the time most viewers today see Casablanca they'll have already seen most of the scenes ripped-offed, parodied, homaged, or referenced. For the first time viewer it won't feel like the original and instead will feel like an old black and white copy with a strange style of overacting.