A pig on a trampoline goes flying toward the screen, his sizable rear end smashing against the glass. A sloth doing yoga ties himself up in knots, leaving his face, as he laments, perilously close to his butt. A cute bunny unexpectedly poops and shakes his tail at the camera.

Moviegoers tuned into this summer’s film slate are well familiar with these animals’ backsides, which arise triumphantly at the ends of ads for the animated films “Angry Birds,’’ “Ice Age: Collision Course,’’ and “Secret Life of Pets,’’ respectively. What’s going on here is rather subtle. OK, not the jokes. And not the alignment between form and content evident in so many tails appearing at the tail end of ads. No, what’s subtle is the message all these butt jokes communicate: These movies are for boys.

Consider 2013’s “Frozen.’’ It’s easy to forget now, but it was initially sold with a bait-and-switch. The ads hid the dueling sisters who were the center of the movie behind the antics of a goofy snowman and cavorting animals. The last image in many commercials? A reindeer scraping its butt on a bed of ice. For the film’s marketers, that comically grim motion played an important role. The beast was removing the whiff of girliness that might drive away boys.

“Frozen,’’ of course, went on to become a huge hit, among both boys and girls, but initially Disney received some flak over this strategy, mostly from critics disturbed by the company’s willingness to pander to sexism and obscure its female heroines but also from at least a few parents who felt tricked into taking their sons to the wrong kind of film.

That blueprint, however, has not gone away. Today’s producers of animated movies still appear more worried about scaring off little boys than about upsetting progressive-minded critics.

Just how obsessed are film marketers with butt jokes? After seeing so many of them in recent years, I decided to answer with my own obsessiveness and put together a spreadsheet. Going solely off TV spots and trailers available on YouTube for American animated films (and hybrids like “The Smurfs’’) from the beginning of 2010 through the end of this year, I found that 66 of 77 put butt jokes in their campaigns. Forty-eight of those followed the formula of putting the joke as the kicker right before the title or the end of the ad.

Indeed, movie studios have gotten it down to a science, and while that’s good for their bottom line, that’s probably just as bad for little boys and girls as it is for comedy.

In his book “Packaging Boyhood,’’ Mark Tappan traces a long pattern of what he calls “the assumption that boys are attracted to crude, silly stuff.’’ In other words, potty humor sells — and marketers aren’t afraid to use it. “This is the trope of boys’ TV, the leitmotif of marketing boyhood,’’ Tappan, an education professor at Colby College, writes.

In 1994, “The Lion King’’ was the first Disney movie to include a fart. It was followed a few years later by the wildly successful, rip-roarin’ “Shrek’’ series, likely cementing the association in marketers’ minds between butts and profits.

But if this is the only way to sell a movie, what does a company like Disney do with its back catalog of butt-joke-free classics? In 2008, according to viewers of Cartoon Network, the answer was to pull a fart out of thin air. That year, commenters on several online animation forums reported seeing a promo for 1961’s “101 Dalmatians’’ in which a shot from the original of a horse’s backside was digitally expanded as a fart noise was added in, followed by one of those Dalmatians reacting quizzically. Other commenters complained about ads in which burps were inserted into the open mouths of characters from “The Jungle Book,’’ “Lady and the Tramp,’’ and “The Little Mermaid.’’

Such humor currently reigns in the children’s book world as well. It seems every discussion of how to get boys to read is answered with an extended butt joke. A 2005 Washington Post piece focused on “The Day My Butt Went Psycho’’; a 2011 Post article suggested “Doctor Proctor’s Fart Powder.’’ A 2008 Wall Street Journal article pointed to the successes of “Captain Underpants’’ and “Sir Fartsalot Hunts the Booger.’’ These articles feature authors, teachers, and bookstore acquisitions directors who all express certainty that boys want “fewer plucky female protagonists and more potty humor and monsters.’’ These butt jokes, they argue, are a gateway drug — the only way to get boys to pick up a book, just as they’re the only way to get them to see a movie about princesses.

Now if you’re thinking girls enjoy these jokes too, you’re right. It’s not that girls can’t laugh at butt jokes, but that girls don’t need them. Studies of viewing habits among boys and girls have repeatedly found girls are happy to partake of “boy-focused’’ movies and books. Yet while girls blithely identify with male protagonists, boys generally refuse to do the opposite. They require pandering — male characters and their humor. For observers like Tappan, such information presents a problem to be corrected, but if you look at how marketers speak among themselves, it’s a road map.

“For those products and programs which are dual-gender targeted, we need to be careful to include elements of appeal to both sexes without turning off one or the other gender,’’ writes Daniel Acuff, president of Youth Market System Consulting, in his instructional book, “What Kids Buy and Why: The Science of Marketing to Kids.’’ “As a general rule, females are more comfortable with marketing approaches featuring males as primary visuals . . . whereas males are not comfortable with marketing approaches featuring female characters as primary visuals.’’

It’s a rule that leaves men front and center. Even as studios like Disney attempt to strike more progressive depictions of girls in their movies, they’re careful to appease the boy audience they need to ensure blockbuster-level sales.

Rebecca Hains, author of a 2014 study of Disney’s impact on girls, “The Princess Problem,’’ highlighted the case of the studio’s 2012 movie “Brave.’’

“Brenda Chapman, who created and directed the majority of it, is herself a mother,’’ Hains said. “It was really meant to elevate this idea of a mother-daughter relationship, which Disney films historically have not had much of; usually the mom is dead. And yet the ads were mostly about the triplet brothers doing wacky things, and I think there might even be at one point one of the men mooning the audience.’’

(“Feast your eyes,’’ a Scotsman shouts as he bends over and lifts his kilt, to the disgust of those behind him. Then, in accordance with the formula, the movie’s title appears.)

Hains suggested it all goes back to a developmental phase called “appearance rigidity,’’ which hits between ages 3 and 6. For girls, it means embracing gender stereotypes, which is great for Disney’s princess marketing. Boys, by contrast, do not embrace anything specific but instead assert their gender identity through the rejection of anything “girly.’’ Hains noted that putting “Princess’’ in the title of 2009’s “The Princess and the Frog’’ may have been enough to scare off boys, although Disney tried to entice them by filling the ads with butt jokes. Since then, Hains said, Disney has “been desperately trying to signal boys, and say, ‘This is for you as well.’ . . . So that’s why you’ll notice if you look at the titles of the more recent quote-unquote girly films, the princess films, they have really active titles. So Rapunzel isn’t ‘Rapunzel,’ it’s ‘Tangled.’ ‘Frozen’ isn’t ‘The Snow Queen,’ it’s ‘Frozen.’ ‘Brave’ is the same.’’

A recent analysis by linguists Carmen Fought and Karen Eisenhauer has shown that while the number of female-centric Disney movies has risen greatly in the last few decades, women’s lines of dialogue in them have actually dropped compared to Disney’s mid-20th-century princess movies. It’s an apparent trade-off: Women get the starring roles again but only in exchange for being crowded around by men’s voices — and farts.

Tellingly, most of the ad campaigns I came across that didn’t feature butt jokes were for action-heavy releases like “The LEGO Movie’’ and “How to Train Your Dragon,’’ films that were already clear enough about their boy appeal without further signaling. But when there’s any room for ambiguity, they squeeze in a butt.

Marketers know what they’re doing. The fear is that when they appeal to stereotypes like this they’re not simply responding to children as they are but further reinforcing gender divisions. Boys’ desire to be different from girls is at least in part just a show, a response to social pressures. Their gender identity is policed more closely by parents, both in terms of play and, later, sexuality. They’re more responsive to which gender is shown using a toy in a TV ad but also interested, if confident nobody’s watching, in trying out girls’ toys. Films and toys are gendered “not because of children’s needs,’’ Hains said, “but because of marketer’s desires.’’ As marketers even admit on occasion, a divided playroom means more toys to buy.

These intense gender divisions are brought forward into adulthood. From smaller concerns like the idea that women can’t be funny and the bizarre aggrievement we’ve recently seen over women starring in the new “Ghostbusters,’’ to the broader gendered hierarchies that still reign in the workplace, the notions of difference inculcated in childhood stick around. And they’re limiting for boys as well. Marketers are working under an assumption, Tappan said, that boys “don’t have access to a wide range of feelings, but the thing that will appeal to boys is crude, potty humor. . . . That’s selling boys short.’’

It starts with selling their parents short, or at least their dads. When watching these ads, I found one for 2013’s “Walking with Dinosaurs’’ that presented it as an elegant CGI nature film, with barely a word — much less a fart — to be heard. I was impressed. Then I watched a 30-second commercial for the same movie that ends with the triceratops heroes facing off against a T-rex in which one admonishes the other, “Remember, they can smell fear.’’ Another responds sheepishly, “Sorry, that’s not fear.’’ The title appears, and then another dino adds, “I think I just stepped in some fear.’’

I remembered seeing this version on TV. Film marketers shrewdly cut different ads of the same movie to appeal to different audiences, and whomever that tasteful cut was meant for, it wasn’t me. I usually only catch commercials during sporting events, a key period for the 18- to 49-year-old male demographic, and the site of many of the ads that prompted this article. Marketers of course aren’t just selling boys on this stuff but men as well. They’re counting on both our own narrowed senses of humor and our narrow understanding of children’s.

Indeed, all this meticulous marketing could make you forget the great thing about both boys and girls: They’ll laugh at anything.

Andrew Heisel is a writer living in New Haven. Follow him on Twitter @andyheisel.