After spending four seasons making one of TV's best shows, The Americans showrunners Joe Weisberg and Joel Fields are pretty confident in their ability to determine what's best for the series. But that all goes out the window when it comes to incorporating period-specific ads and other pop culture references into the FX drama about two Russian spies (Keri Russell and Matthew Rhys) undercover as a suburban D.C. family in the early '80s.

"We work from a place of fear, and in general, we work very hard not to work from a place of fear," said Weisberg. "But we're very worried about hitting things too much on the nose. It's so easy with pop cultural references to be screaming, 'Here we are in 1983! Here we are with the thing that everyone remembers and knows signifies the time period!' We're really careful not to do that and be so judicious when we hit the big ones."

They saved one of "the big ones" for Wednesday's episode, the seventh of Season 4, called "Travel Agents." During one scene, two teenage boys bond while watching one of Brooke Shields' iconic Calvin Klein ads, which featured her whistling "Oh My Darling Clementine" and then saying, "You want to know what comes between me and my Calvins? Nothing."

Shields' Calvin Klein campaign was one of the most famous of the decade, but it only amounts to a few seconds of screen time on The Americans. That puts it squarely in Weisberg and Fields' "less is more" approach to featuring pop culture.

"When we hit the big ones, we try to do it either directly through the eyes of our characters or, if not, then very much in the background," Fields said. "We would rather something live unnoticed in the background and hit our audience in their subconscious than we would have it be featured and distract them. So the goal is actually to never really have the pop culture pop, but have it just capture the truth of the period that the show is existing in."

When they plotted the scene in which Henry, the son of Rhys and Russell's Philip and Elizabeth Jennings, and Matthew Beeman, the son of their neighbor—and the FBI agent on the Jennings' trail—Stan Beeman (Noah Emmerich) talk about an attractive girl on TV. "Joe and I both were, let's say, conscious in those days, and we remember who boys talked about in that way. So it was not a long throw to get to Brooke Shields and 'Nothing comes between me and my Calvins,'" said Fields. "What we want is for it to always be integrated into the show so that there's never the sense that the show is stopping for some fun pop culture reference, but rather they come out through the characters' experiences."

Last year, however, the show featured an ad that more directly tied into a storyline: for Love's Baby Soft feminine products, possibly one of the most disturbing commercials that has ever aired. (The creepy voiceover notes that the product has "the innocent scent of a cuddly, clean baby … that grew up very sexy.")

The ad touched on one of Season 3's arcs in which Rhys' character is forced to seduce a teenager who's the same age as his own daughter. "As we were breaking that story, one of the writers ran screaming into the office one day. 'You're not going to believe the commercial I just found! It's real!'" said Fields.

A year earlier, the duo incorporated a famous local Washington, D.C., ad for the Jhoon Rhee martial arts studio. "Anyone who lived in D.C. recognized that commercial," said Weisberg. "Local commercials are really interesting because if you're not from the area, you don't recognize them, and if you are, they're almost bigger than the national commercials because there's a little bit of pride in your area."

But not every ad Fields and Weisberg want to use on The Americans ends up making the cut. The producers considered using a Taster's Choice coffee ad playing up its use on NASA's Columbia space shuttle. "It's a fantastic commercial with a floating coffee cup, and just the animation is so 1984. But it's just never happened for the show. We looked at it, but then we thought, 'Is it trying too hard?'" Fields said.

Then, when they did talk themselves into using the Taster's Choice ad, they couldn't get the rights to use it. "On some of these commercials, rights become a challenge because they got certain rights but not all rights, and we can't find the [correct] people," said Weisberg.

Weisberg and Fields are breaking their usual rule about not putting pop culture events front and center on The Americans with the next episode, which is called "The Magic of David Copperfield V: The Statue of Liberty Disappears" and includes a scene in which the Jennings family watches an April 8, 1983 special in which Copperfield made the U.S. landmark seem to vanish.

A future episode will center around another major '80s TV event: The Day After, the chilling TV movie about the aftermath of a nuclear war between the U.S. and the Soviet Union. ABC estimated that more than 100 million people watched the original broadcast on Nov. 20, 1983.

"You've got that juxtaposition … you've got the David Copperfield moment, and we've got The Day After," Weisberg said. "One is about as gloomy, depressing and horrible as you could imagine, and one is really uplifting and great and fun and the American spirit in the best kind of way. So for us to have both on the show—and it's easy to turn them into different moments because the Jennings family and the Beeman family would really sit down in the living room and watch both of those. We don't have to hide those in the background as if to show that they happen to be watching it. It really makes sense to make it center stage."

While another month's worth of Season 4 episodes remains, Fields and Weisberg are already well into planning Season 5 and have finally come to a decision whether they will need one or two more seasons to wrap up the Jennings' story.

"I don't know that we have a final nod from the network, but we feel like we know what we'd like to do, and pretty soon, we hope to be able to talk about it," Weisberg said. "But we've got a very strong handle on it."