Famed quote brought about by actor Harrison Ford's frustration with numerous retakes of that scene on Bespin from The Empire Strikes Back, moments before Darth Vader has Han Solo frozen in carbonite. Ford sarcastically adlibbed Han's now-beloved response to Princess Leia's declaration of love and creator/producer George Lucas left it in, since he thought the scene read better with the changed line. (The original line was "I love you too.")
Ford's impatience had also changed the script in Raiders of the Lost Ark, thanks to a case of dysentery. Instead of a long battle with a sword-wielding enemy, Indiana Jones simply shoots the guy. Classic. Like Indy's shooting gag, the "I love you." "I know." dialogue was later reversed in the next sequel, Return of the Jedi, with Leia (Carrie Fisher) getting the lovingly semi-sarcastic response. Of all of the great lovers in movie history, Han and Leia stand out, mostly because of this brief exchange of dialogue, which completely sums up their relationship.
No matter what your opinion of the Ewoks is, you've just gotta love Leia's smirk during the rehash on Endor.