Green Arrow, the Atom and the Flash have trounced supervillains, saved countless lives and brought relative peace to their world. Now there’s a new task they are slowly accomplishing: Keeping advertisers’ products from showing up in their TV programs.

When “DC’s Legends of Tomorrow” airs this evening on the CW, viewers won’t see Ford vehicles turn up while Hawkgirl, Firestorm and White Canary zoom about on screen. But they will see Ford cars during a commercial break, when the car manufacturer unveils a promotion that lets “Legends” viewers explore three different “fan art” murals (pictured, above) over the course of the rest of the TV season. Viewers will be prodded to go online, where they can see longer videos about the artwork and even get clues about the show’s storylines. Brandon Routh, who plays Ray Palmer (also know as the Atom) on “Legends,” will be featured in one, and others will boast Franz Drameh, who as “Jax” Jackson shares the body of Firestorm, and Ciara Renee, who plays Hawkgirl.

“We’ve been there, done that,” said Barbra Robin, the CW’s senior vice president of integrated marketing, speaking of the popular TV-advertising practice known as product placement. “It’s always been a little bit awkward.” Indeed, many of the promotions tied to CW’s growing slate of superhero shows feature advertisers making reference to the programs in the confines of the commercial breaks – not in the show itself.

The superheroes appear to be leading a new charge. For years, the practice of jamming logos, cups of cola and close-ups of gadgets into TV shows and scripts was de rigueur – the result of TV networks trying to capture ad dollars as rival technologies hooked sponsors’ attention. Now, TV-network executives and advertisers are pressing for something more sophisticated than having the “Modern Family” character Hayley Dunphy, played by Sarah Hyland, getting a new Toyota. Such stuff is still in demand, but it can be clunky and distracting. As TV networks try their hand at more fantastic concepts, placing sponsors’ goods on set and in plots may not be received as well.

Getting Aquaman to guzzle a sports drink or text a pal on a particular device can be tough going. In advertising circles, it’s well known that DC Comics, the Time Warner unit that oversees characters ranging from Supergirl to Mr. Freeze, is very particular about how its characters are portrayed, and for good reason: Fans scrutinize every aspect of the way a character is presented on TV, on the movie screen and the comic-book page. What’s more, the shows often take place in strange environments that don’t lend themselves to natural product appearances.

“These shows have their fans and their stories and their myths, and you can’t mess with that,” said Linda Rene, executive vice president of prime-time sales and innovation at CBS.

The same can be true of many shows set in exotic locales. Viewers never saw a Microsoft Surface or a Chevrolet turn up on ABC’s “Lost.” How would such things turn up on a remote island or in one of the series’ many time jumps? When CBS ran “Extant,” set in the future, placing a product in the story would have been challenging, said Rene. “You had to imagine your product, and what it would look like, and how people might behave with it 50 years in the future. We could not really crack that code,” she said. “If you are dealing with something that’s not of this world, it’s harder.”

Just as Superman might succumb occasionally to Kryptonite, so too are some TV heroes prone to letting something slip past their defenses. AT&T has placed its devices in CW’s “The Flash,” while Toyota Motor’s Lexus has cruised through “Marvels’ Agents of SHIELD” on ABC. More often than not, however, the heroes resist the temptation, and spur the creation of new models.

With its new alliance with CW’s “Legends,” Ford has helped build two superhero pacts. Over at Fox, Ford has sponsored “Gotham” for two seasons. Because the city of the title is portrayed as being filled with vintage automobiles, weaving a new Ford vehicle into the mix can be daunting. Ford placed more emphasis on vignettes that appeared during the drama’s commercial time. The videos featured members of the cast, such as actor Cory Michael Smith preparing for his role as Edward Nygma, who develops into the villain known as the Riddler. The automaker’s vehicles are put on display in a more believable setting. TV viewers saw an edited version of the video on TV and an extended one online.

Ford executives believe the superhero dramas and other programs with sci-fi themes attract healthy swaths of millennial viewers, said Kathleen Kross, Ford Motor’s car media integration manager. “The shows don’t lend themselves to in-show product placement, but that doesn’t mean we at Ford don’t see the value of the audiences watching the show,” she said.

The CW has built other team-ups between sponsor and superhero. Activision wanted to promote the launch of a new version of “Guitar Hero” last year in “Arrow” and “The Flash.” Yet having the characters in the shows play the game did not seem likely to work in either show’s storyline, said Robin. Instead, actors from the shows took part in “Guitar Hero” competitions for “Team Arrow” or “Team Flash” in ad breaks. AT&T has sponsored weekly “fan talk” recap shows for “The Flash.”

One factor in the rise of the commercial-break super-adventures, said Robin, is that producers and writers involved in comic-book shows are accustomed to having a lot of story to tell. Striking these deals with advertisers can help them generate additional plot points that keep viewers interested. “Because they are comic-book people, they have so much more to say than could ever make it into an episode,” she said.

CBS is banking on the setting of “Supergirl” to help it buck the nascent trend. Unlike other superhero showcases, “Supergirl” doesn’t hinge on time travel or an odd setting, said Rene. “We have had many discussions about doing integrations with’ Supergirl.’ Our show is grounded in reality. It’s set in National City. It’s kind of like downtown L.A.” she said. “We drive normal cars in ‘Supergirl.’ They use normal technology in ‘Supergirl.’ They probably eat at fast food restaurants in Supergirl.”

Will this heroine find new, in-show support from Madison Avenue before her enemies can strike again? For comic-book fans, the answer is simple: To be continued.