Michael Weatherly and Cote de Pablo’s dynamic on NCIS: Tony & Ziva isn’t entirely fiction.

The actors recently brought back their beloved characters for the long-awaited spinoff series, and they tell PEOPLE that they were just as excited as their fans to be back on screen together. After eight seasons on the original NCIS, Weatherly, 57, and Pablo, 45, say they have integrated their real-life banter into the show.

“That’s what I love so much about working with Cote,” the Bull alum says. “Because sometimes the next line that comes out of my mouth is, ‘I have no response to that,’ or, ‘I don’t know what to say.’ Then that’s not what was written, but it ends up being in the show, because that’s Tony’s response to Ziva, which is like, she has his number, and he has her number.”

Michael Weatherly and Cote de Pablo in NCIS.Richard Foreman/CBS via Getty

“If somebody came up to me or Cote, like a director or a writer, and tried to tell us what our character was thinking or feeling, that was a bad idea,” he adds.

While they both acknowledge their ability to improvise in that way “is unusual,” the duo praises their directors for allowing them to take the reins. When they began filming Tony & Ziva with a new set of costars, Weatherly reveals he tried to cultivate the same energy on set.

“We would all mess with each other,” he admits. “You have to find the fun.”

Pablo then quips: “You have to fun it up.”

“Yeah. If somebody doesn’t like saying ‘Mr. Sivapatha Sindaru,’ you got to be like, ‘What was the name?’ You’ve got to make him say it again, even if it’s not scripted,” Weatherly laughs.

He says that part of what makes Tony & Ziva such a “beautiful sequel” is that the cast, although less familiar with their characters than Weatherly and Pablo were, always brought “their own energy and light” to the story.

Cote de Pablo and Michael Weatherly.Marcell Piti/Paramount+

One scene that he recalls going entirely off-script occurs in one of the first episodes, where Nassima Benchicou’s Martine holds a gun up to Tony’s neck.

“I remember when we were shooting, it wasn’t in the script,” he explains. “She just did it. I was like, ‘That’s not in the script. What are we doing? What are we doing with the gun? What are we doing?’ Now, it was a plastic gun, but she was like, ‘How can I make Michael Weatherly uncomfortable?’ Or, ‘How can Martine make Tony DiNozzo uncomfortable?’”

“These things blur when you’re working,” he notes. “But that requires trust, faith in the process and in the whole creative endeavor, and everybody was game.”