An actor’s body is their instrument, and depending on one’s versatility, that instrument can produce all kinds of music. To cite a pair of extreme examples, Robert De Niro famously packed on 70 pounds to play post-retirement Jake LaMotta in “Raging Bull,” while Christian Bale dropped 60 pounds to play the emaciated main character of “The Machinist.”

For the most part, though, actors are cast according to physical type, which means they shouldn’t have to drastically alter their appearance to play a specific role (because there’s a bevy of talented actors who fit a variety of types). Still, there are parts that require rigorous training, like action movies. If you’re going to play a character who can take out multiple adversaries at once with their bare hands, you’ve got to look convincing on camera. This means loads of combat training in different martial arts disciplines. Above all, this means getting in shape.

For an actor who’s been cast as a superhero, this means toning up that bod so you can fit in an unforgivingly tight spandex suit. This can be incredibly daunting. Just ask Scarlett Johansson, who had to slip into the form-fitting costume of Natasha Romanoff, aka Black Widow, for the first time in 2010’s “Iron Man 2.”

A perfect fit in the Marvel Cinematic Universe

Back in the late 2000s, Johansson was best known for her dramatic work in films like “Ghost World,” “Lost in Translation” and “The Prestige,” but she wasn’t altogether new to action movies. She’d played an escaped clone in “The Island” and donned a variety of slinky outfits in “The Spirit.”

She had not, however, had to pour herself into a superhero costume meant to accentuate her athleticism as well as her beauty, and she found this incredibly daunting. As she told Sci-Fi Movie Page in 2010:

“I knew it was going to be some kind of sexy unitard, because I had researched the character in the comics. I’ve never worn anything like it before, so I had a freak-out moment that lasted about half a day, but then I said ‘Okay, time to suck it up’ and just went full force into getting in shape to wear the costume and perform the physical action so it looked just right.”

Funnily enough, I was one of a lucky few journalists who got to talk to Johansson on the set of “Iron Man 2,” and there’s a gif that documents my impressed reaction (I’m the balding doofus in the center of the frame).

She had a great sense of humor about flaunting her form, like a model walking a runway, and clearly learned to embrace the hit-the-gym discipline necessary to keep her in peak Black Widow shape over the next decade.

While I’d much rather see Johansson showing off her acting chops in a meaningful film like “Marriage Story” or “Asteroid City,” you can’t fault her for broadening her audience by joining the Marvel Cinematic Universe.