It’s Valentine’s Day, and maybe you’ve got a sweetie within earshot or eyesight. (If you don’t, listen, forget the whole thing — it’s a fake holiday anyway, cooked up by florists and the greeting card industry.) Remember when you guys were first hitting it off, striking sparks that felt like the first in recorded human history? Remember when you realized it was serious — like, meet-the-parents serious — and that you were actually contemplating spending a life with this person?

That’s when you had to sit them down and make them watch the movie. You know the one I’m talking about. The deal-breaker, the Love Me, Love This Movie movie. The film you cherish way too much, and if Mr. or Ms. Wonderful doesn’t like it . . . well, maybe they’re not so wonderful after all.

This sounds superficial, but, trust me, it isn’t. You’re facing the possibility of decades together — children, grandchildren, Florida. If you love “The Royal Tenenbaums’’ or “The Notebook’’ and he or she doesn’t, this isn’t a minor parting of taste. This reflects a profound philosophical schism, and you’re probably better off breaking up. No, really.

Back in the mid-1980s, I started dating a woman I’d known casually in college and had become reacquainted with in New York. She was beautiful, accomplished, literate, hot — man, was I out of my league.

Our first movie dates were exploratory, as these things are. We saw Spike Lee’s breakthrough, “She’s Gotta Have It,’’ Rob Reiner’s “Stand By Me,’’ a freaky horror film called “From Beyond,’’ by the same team that had made the gonzo 1985 gore-comedy classic “Re-Animator.’’ She stayed in the lobby for most of that one. But she stayed.

Eventually, though, I sat her down for the litmus test: her, me, a TV, a VCR, and a copy of “Pee-wee’s Big Adventure.’’

What, you thought I was going to say “Citizen Kane’’ or “The Godfather’’? Those are the acknowledged warhorses of cinema, and if you don’t like them, that’s your business. But in 1986 — years before his little scandal — the humor of Paul Reubens, a.k.a. Pee-wee Herman, was a decidedly acquired taste. Either you laughed helplessly at the pure silliness of lines like “Let’s talk about your big ‘but,’?’’ or you had contempt for the whole thing, like The New York Times critic Vincent Canby, who famously poured vitriol on “Adventure’’ and ended his review with the words: “You have been warned.’’

He didn’t get the joke, obviously. But would my lady friend? She was a lawyer, it was the ’80s, she had serious hair and power shoulders. Could she still tap into her infantile side enough to appreciate a grown man wrapping his face in Scotch tape and yelling, “I know you are, but what am I?’’

Recently I conducted an informal poll of online friends and family, throwing the question out there. What was your deal-breaker movie? At first, I was surprised by how many people came back with a comedy. “Airplane!,’’ “Duck Soup,’’ “The Hot Rock,’’ “Annie Hall,’’ “Harold & Kumar Go to White Castle.’’ But on second thought, this makes complete sense. Comedy is personal. What makes us howl at one thing and sit stone-faced at another is probably decided at the level of genetic algorithms. In romance, the genes have to match in all the least obvious ways. Would you want to share the rest of your days with someone who doesn’t think “Monty Python and the Holy Grail’’ is funny? I didn’t think so.

I also heard about certain cult films and art-house classics that hit the respondent at a tender and impressionable age. “Amelie,’’ “Jean de Florette,’’ and “Les Enfants du Paradis,’’ came up a lot. Also “Harold and Maude,’’ because if you and your beloved can get on the same page regarding a wonderful black comedy about suicide and intergenerational romance, you deserve each other, and your children deserve you.

“Casablanca’’ is a handy clearinghouse item; in the words of one friend: “I finally got her to see it; she did not like it. (‘It’s stupid.’) I have not seen her since 1985. She was gorgeous, but I can’t say I miss her.’’ This goes both ways, interestingly. Another friend went to a John Hughes movie, the woman loved it, he hated it, and that was that. Call it a reverse dealbreaker.

It can get granular. My critical colleague Peter Keough says of his dealbreaker movie, the 1986 comedy “¡Three Amigos!,’’ “Extra points if there’s laughter at Martin Short’s story about Dorothy Gish told to the bewildered Mexican children.’’ My buddy Clif says his wife “passed the test when she named the band doing the Bowie cover in ‘Something Wild.’?’’ That band was The Feelies; now I want to marry her.

Our deal-breaker movies say things about ourselves that we could never express otherwise. Cueing up “The Princess Bride’’ signals that you prefer your romantic cheese simultaneously parodied and served straight — a tough concept to articulate. My high school friend Greg says his deal-breaker is “Slapshot,’’ a terrific film that requires one to appreciate the game of hockey and the great joke of it as well.

Some choices seem perverse, but only on the surface. I heard about a guy who took all his dates to screenings of the disgusto midnight-movie staple “Pink Flamingoes’’ — “If they could stand it, they were in.’’ I heard “Repo Man,’’ “Face/Off,’’ Tarantino’s “Death Proof’’ (the girlfriend in that case made him watch “Mean Girls’’; they both passed with flying colors). I heard from a woman who loaded up her future husband with gruesome classics like “Night of the Living Dead.’’ (“It wasn’t that he needed to love them, but I felt that he couldn’t understand me without watching these films.’’) I heard from a friend who recalled the illicit thrill of his leg touching another man’s during a college showing of “Blade Runner’’; 30 years later, they’re still together.

It’s always a gamble, and if it pays off, it can seem like a miracle. To go back to that evening in the mid-1980s, I can’t begin to convey my relief as my sophisticated lawyer love’s power shoulders shook with laughter at every idiot joke in “Pee-wee’s Big Adventure.’’ The breakfast scene, the trip to the Alamo, Large Marge — all of it. The deal was set, the die was cast; two kids and many big adventures later, we’re about to celebrate our 25th wedding anniversary.

Happy Valentine’s day, dearest. Are you glad for where Pee-wee and company have taken us over the years? I know you are, and so am I.

Ty Burr can be reached at ty.burr@globe.com.