Chatter about Catastrophe, a series that airs on regular TV in the UK and streams on Amazon in the US, often concentrates on how gleefully frank and filthy it is. Written by its stars, Rob Delaney and Sharon Horgan, the show follows a American man and an Irish (sorry! originally said "British"; I'm a distracted American) woman whose fling leads to a pregnancy, then a marriage and a love affair, in that order. Season 1 traced them from the moment they met through the moment she went into premature labor; season 2, which debuted on Amazon on April 8, is about parenthood, though the opener finds her still pregnant — there's an explanation, don't worry.

Indeed, one of Catastrophe's joys is that whether the topic is sex, pregnancy, childbirth or matters toilet-related, it's consistently plain-spoken and brutal — sometimes for laughs, sometimes because to be otherwise would be dishonesty by elision, and maybe sometimes because there are new stories to tell when you expand the field to places lots of people either can't play or decide not to.

Just as important, though, is the fact that Catastrophe is, in its particular, everybody-poops kind of way, deeply romantic. While it's not especially unusual for romantic comedies to successfully be both romantic and funny, this one is special because humor inside the story is a large part of the reason it's romantic. It uses laughter within scenes — Horgan's especially — to underscore that Sharon and Rob are in love, but even more that they are on the same side, and aren't the kind of bickering people who will eventually make an audience wonder why they're together at all.

An example: The season 2 premiere soon finds Sharon and Rob having a fight, which ends abruptly when he crawls into bed, she tells him not to touch her, and he says, "If you come anywhere near me, I'm going to scream." Facing away from him, Sharon laughs, and the fight is over.

Cracking up generously doesn't apply only to ending fights; it's their currency and their common language. There's another moment in the first handful of minutes of the premiere in which pregnant Sharon has gotten Rob's attention by faking an emergency. Her defense, which turns in seven words from insisting she wasn't deceiving him to admitting she was: "I genuinely felt really lonely and bored." This isn't just clearly funny to him, but it's funny to her, too. They're together physically but also together emotionally, and the shared chuckle is an economical way to communicate that.

The frequent deployment of in-scene laughter in Catastrophe solves a common problem with relationship comedies, which is their tendency to feel transactional. People seem to be performing the relationship more than being in it, and contrary to every close relationship — romantic or otherwise — scenes generally either sit in one spot to make a point or they move along a straight line. Either any given scene is loving, or it's playful, or it's an argument, or it's a scene where people make up according to predictable rhythms of apology and forgiveness.

Catastrophe scenes, on the other hand, often shift unpredictably — there's a fight in a restaurant later in the season that totters dangerously then swerves — so that teasing turns ugly, or fights are resolved, very often using this shorthand of when you laugh and when you don't. Horgan in particular has a huge vocabulary of laughs in the scenes the two do together: a bare chuckle that sits on top of her dialogue; a light, delighted laugh at the end of her own jokes; a satisfying, raucous guffaw.

And here's the thing Catastrophe understands about Sharon and Rob: this is something they want out of this relationship, a lot. This is part of why they're in love: they laugh at each other's jokes constantly. In both of them, there is a performative streak that needs a response. That's who these people are, and to suggest they could genuinely fall in love with anyone who didn't give them that wouldn't feel like the truth. They both find humorless people utterly tiresome, and if they didn't create these feedback loops of laughing and pressing harder on the joke until it breaks and laughing more, you wouldn't believe they could even be friends.

It's a particular challenge of romantic comedy specifically that people in comedies are usually not supposed to act as if they know they're in comedies. That often means they don't laugh at the things that are happening that are funny — if anything, they laugh uproariously for effect, for the creation of a raucous bonding scene, at things that aren't particularly funny. "Friend laughs at friend" is usually a plot point — they're hanging out, they're having fun. Catastrophe is good at remembering that laughter is the appropriate natural response to things that are funny, even if they're written into a script as jokes. For instance, at a party, Sharon makes a joke about her mother-in-law (Carrie Fisher), and her friend Melissa (Sarah Niles) just cracks up as Sharon walks away, not because Melissa laughing is all that important to the scene, but because it makes them feel more like real friends and real humans. A real person laughs in that scene, particularly a real person who would ever be friends with Sharon.

Even in friendships, it often limits storytelling if you don't let people laugh at jokes. Consider the scene in When Harry Met Sally when Meg Ryan, Carrie Fisher and Lisa Jane Persky sit around talking about men. When Fisher responds to news that a potential prospect in her card file (hello, 1989!) is married, she folds down the corner of the card. It's a joke in the movie, but her friends don't laugh. Why don't her friends laugh? A normal person would consider that a funny thing to do. They don't laugh because people in comedic situations are often not supposed to notice they're comedic. It makes the scene feel a little distant, funny but not all that warm.

Compare that to the deeply flawed Reality Bites, which, for all its deep flaws, builds a very nice friendship between the characters played by Winona Ryder and Janeane Garofalo. There's a very serious talk about AIDS testing in which Garofalo's Vickie admits that she's terrified that she's dying and she'll wind up having a funeral like something out of Melrose Place. Ryder's Lelaina comforts her and then says, very unexpectedly, in the same enormously sympathetic voice, "Melrose Place is a really good show." In many comedies, this would just be a funny line from the outside; here, it's also a funny line inside the movie, and Garofalo's face gradually breaks into a grin — it's the moment that breaks the tension. Feeling comfortable enough to make that joke in that moment, knowing it's a joke and expecting your friend to laugh, is part of that relationship. To replace the grin with an eye-roll or a sad nod would be more traditionally of the school of "even in character, you don't acknowledge jokes," but it would make the scene fundamentally different, and it would leave the characters much less close.

By following models where the characters don't notice jokes — by prohibiting them from laughing at laugh lines — lots of romantic comedies rob themselves of one of the primary ways people create connections and one of the ways close relationships are navigated and negotiated. Rob and Sharon use laughing as glue, as distraction, as entertainment, as team-building, and ultimately as reassurance to each other that in a world full of battles towering and stupid, they mean to be working together. It happens in Before Sunrise, too, and when Bill Hader yells for the check in Trainwreck. It's very useful in demonstrating the part of every close relationship that's about becoming allies, or realizing you can be allies.

And nobody needs allies, you might notice, quite like new parents.

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