When the producers of the FX series “The Americans,” an espionage thriller set in the early 1980s, began preparing a story line about the government’s covert efforts to help contra rebels in Nicaragua, they wanted to consult with someone well versed in this chapter of recent history.

So they reached out to colleagues within Fox, the parent company of FX, and were soon connected to an expert with unique firsthand knowledge: Oliver North, the former Marine Corps lieutenant colonel and National Security Council aide, and a central figure in the Iran-contra scandal.

Mr. North provided the producers of “The Americans” with so much detail and color for the April 23 episode that he was rewarded with a story credit. In that episode, the show’s main characters — a pair of K.G.B. spies (Keri Russell and Matthew Rhys) masquerading as a wholesome couple in suburban Virginia — try to infiltrate a contra training camp on American soil.

But with Mr. North’s involvement comes the potential for a whirlwind of controversy; questions about why he should be allowed to benefit from his notoriety; and the possibility of opening political wounds that have not healed after 30 years.