I think this is the beginning of a beautiful friendship.

Shmoop agrees. The last line of Casablancacould serve as a perfect first line of When Harry Met Sally. This movie really is about a beautiful friendship… that just so happens to turn into a love story.

Armchair Movie Critics

Casablanca is the subject of Harry and Sally's first real argument. That's right—before they're debating the possibility of men and women being friends, they're having it out over whether Ingrid Bergman's character in Casablanca wanted to be with Victor Laszlo or Rick Blaine.

If you're one of the two people on earth who hasn't seen Casablanca, here's the skinny: Isla (played by Ingrid Bergman) was once madly in love with Rick Blaine (that would be Humphrey Bogart). But the two were torn apart by an unfortunate little thing called World War II. She, as it turns out, is married, to a man whom she thought was dead but, um, isn't. So when Ilsa and her husband show back up in Rick's life, she has to choose between her one true love (that would be Rick) and her nice-but-boring-but-very-good husband, Laszlo. She chooses Laszlo.

Here's how Harry and Sally see it:

SALLY: You're wrong.

HARRY: I'm not wrong, he wants...

SALLY: You're wrong.

HARRY: ...he wants her to leave that's why he puts her on the plane.

SALLY: I don't think she wants to stay.

HARRY: Of course she wants to stay. Wouldn't you rather be with Humphrey Bogart than the other guy?

SALLY: I don't want to spend the rest of my life in Casablanca married to a man who runs a bar. I probably sound very snobbish to you but I don't.

HARRY: You'd rather be in a passionless marriage.

SALLY: And be the first lady of Czechoslovakia.

HARRY: Than live with the man you've had the greatest sex of you life with, and just because he owns a bar and that is all he does.

SALLY: Yes. And so would any woman in her right mind, woman are very practical, even Ingrid Bergman, which is why she gets on the plane at the end of the movie.

This argument perfectly encapsulates the Harry-Sally dynamic—at least, at the beginning. See, Harry thinks that Rick Blaine is the one who's driving the decision here: "He puts her on the plane." For Harry, it's all about Rick's noble and romantic sacrifice. (He did say he has a dark side.)

For Sally, though, it's all about Ilsa taking control of her own destiny. She's not at the mercy of the men in her life—she makes the decision for herself, and a practical one at that.

These viewpoints get mirrored a scene or two later, when Harry and Sally argue about the possibility of men and women being friends. Sally's sexless, practical approach says that they can. Whereas Harry's passionate but pessimistic worldview says no dice.

A Change of Heart?

Casablanca pops up again in the middle of the movie, when Harry and Sally are knee-deep in friendship. As they both sit alone in their respective beds, the screen splits in two and we watch them chat on the phone:

SALLY: Hello.

HARRY: You sleeping?

SALLY: No, I was watching Casablanca.

HARRY: Channel please.

SALLY: Eleven.

HARRY: Thank you, got it. Now you're telling me you will be happier with Victor Laszlo than Humphrey Bogart?

SALLY: When did I say that?

HARRY: When we drove to New York.

SALLY: I never said that, I would never have said that.

HARRY: Alright, fine. Have it your way.

Aw, look how far these two have come. Sally's loosened up enough to realize that Ilsa totally belongs with Rick. (Notice, of course, how she conveniently forgets that she ever argued otherwise). And Harry's mature enough to know that arguing with Sally is pretty useless at this point.

A few moments later, as they watch Casablanca's closing scene, with the iconic line about friendship, Harry says "Mmm, best last line of a movie ever." We're inclined to agree, but we're also big fans of "Right."

What's in a Movie?

So why Casablanca?

The movie serves as a sort of touchstone for Harry and Sally—and the viewers as well. It's not that their lives parallel those of Rick and Ilsa. In fact, their story couldn't be more different. But their return to the movie after establishing a friendship indicates how much these two have changed in the course of knowing each other. And the movie's subject matter provides the perfect fodder for a couple of friends to bicker over the nature of sex, love, and what it means to live happily ever after.

Plus, there's the fact that Casablanca is one of the most enduring romance movies of all time. Sure, it's not a rom com, but any movie that wants to call itself a romance—comedy or no—owes a little debt to Casablanca and its ilk. And now that When Harry Met Sally is a classic in its own right—thanks, in part, to its hilarious musings on Casablanca—it can take its seat on the shelf next to this titan of the romantic genre.