"Greed is good"
Actual quote: "The point is, ladies and gentleman, that greed, for lack of a better word, is good. Greed is right, greed works." – Michael Douglas (Wall Street)



"Play it again, Sam"
Actual quote: "Play it once, Sam, for old times' sake, play 'As Time Goes By'." – Ingrid Bergman (Casablanca)
Actual quote: "You played it for her, you can play it for me. ... If she can stand to listen to it, I can. Play it." – Humphrey Bogart (Casablanca)
Note: Woody Allen paid homage to Casablanca under the title Play It Again, Sam, which is likely the source of much such misquotation.
The line first occurred in the Marx Brothers' film A Night in Casablanca (1946), another possible source of the misquotation.