By the time Joss Whedon reunited the ensemble for Avengers: Age of Ultron, Scarlett Johansson had played Black Widow, a.k.a. Natasha Romanoff, in three Marvel films.

During filming, Johansson was pregnant with her daughter, Rose Dorothy Dauriac.

The cast and crew of Avengers: Age of Ultron debated how they would conceal her pregnancy for the film. According to Joss Whedon, no sequences were cut. Three Black Widow stunt doubles, close-ups, concealing clothing and angles, and visual effects were used to make it work.

Chris Evans, who plays Captain America in the Marvel series, remarked during an interview with ABC’s Chris Connelly for “Nightline,” “I’ve never met a woman more happy pregnant than Scarlett,” before turning to Johansson and continuing, “You literally were in the best mood, you were just so happy.”

Robert Downey Jr., who plays Iron Man/Tony Stark in the film, adds, “Great job being pregnant for the whole shooting.”

Over the weekend, E! News reporter/producer Will Marfuggi spoke with the stars of the film, including Johansson and Mark Ruffalo, who discussed how Johansson’s pregnancy impacted production.

“I did as much as I could do and filled in all the blanks later on,” Johansson remarked. When she couldn’t film a scene, one of three stand-ins would cover their faces with dotted maps. Visual-effects artists used the dot maps to graft Johansson’s visage onto their bodies in post-production.

“I have a really amazing, amazing stunt team around me. My stunt double, Heidi Moneymaker—and that’s her real name—is really incredible, and this time took a lot of the punches for me, literally,” she added. “This is like our fourth or fifth movie together, so we kind of have a seamless thing between us.”

The “physical part” of Marvel flicks appeals to Johansson. “I like the fight choreography stuff and getting new weapons,” she said. “I’m pretty active.”

Chris Evans told E! that having so many Black Widow stunt doubles on filming was a weird experience:

“It’s always funny. You walk by, ‘Hey, Scarlett—oh, weird. You’re not Scarlett at all. Sorry.’ A lot of fake Scarletts around.”

The eleventh film in the integrated series, “Age of Ultron” will be the second to include all six of the action elite, who sat down for a chat with “Nightline” to discuss the new film and what occurred on behind the scenes.

During filming, Johansson’s co-stars rallied behind the 30-year-old actress, who gave birth to a daughter shortly after main production wrapped.

“On the last day of shooting, she could barely put a sentence together, but she timed it perfectly,” Evans said.

“Robert [Downey, Jr.] was like, ‘you’re going home now,’” she said.

Johansson added that being pregnant during filming was “great,” but that she was fortunate to “have a very cushy, delightful job that I loved to go to every day.”

Johansson was able to engage with Mark Ruffalo in a fresh way in the film, which is a sequel to 2012’s The Avengers. “None of us had gotten to experience that before, to really interact with him as The Hulk and see Banner behind The Hulk, and then it was Mark there doing it,” she added of his role, which was constructed using a combination of stop-action, stop-motion capture, and CGI technologies. “It was really cool.”

Ruffalo shared this sentiment. “Before, the first time, I was doing it all alone, and the physical movement of the body was completely different than the facial capture. So I had to sit still and do all the face acting in a room by myself to…many cameras, and this time I got to do it all put together with actors,” he shared.

Scarlett Johansson’s solo film, Black Widow, is only now being launched, and the actress says it’s not too late; in fact, the time is ideal.  Meanwhile, Johansson is nominated for TWO Academy Awards this year. It’s her first time being nominated.