How bodysuits are designed to look realistic in movies & TV

• Bodysuits let actors go through physical transformations that they couldn't easily make on their own, from gaining weight to gaining muscle to being pregnant.
• Special makeup effects artist Kevin Yagher of Kevin Yagher Productions Inc. was tasked with creating plausible muscle and fat suits for actors Keanu Reeves and Alex Winter.
• Besides making sure bodysuits fit actors perfectly, Yagher needs to make sure that they look like real human skin with the right colors and texture and that they move the way an actual human body would.

Following is a transcript of the video.

Narrator: This is special effects legend Kevin Yagher.

And here, he's adding some color to the nipple of this fake bodysuit.

But as he moves the airbrush up, he's adding a much more subtle change. You can see the difference between the bottom of the suit and the top part that he hasn't gotten to yet. What this spray paint does is give the suit texture, mimicking the undertones human skin naturally has and giving the appearance of tiny details like pores.

From a life cast picking up on an actor's defining features to sculpting subtle veins to mastering a jiggly stomach, a lot of effort goes into making the bodysuits actors wear look realistic.

Warning: Some spoilers ahead for "Bill & Ted Face the Music."

Bodysuits let actors go through physical transformations that they couldn't easily make on their own, from gaining weight to gaining muscle to being pregnant.

There are times when bodysuits don't need to be as detailed because they're covered in clothing, like this suit Kevin Yagher designed for Dana Carvey in an ultimately cut sequence from "The Master of Disguise."

But because Keanu Reeves and Alex Winter appear shirtless in "Bill & Ted Face the Music," both the muscle suits and fat bodysuit created for scenes where they meet future versions of themselves had to be incredibly detailed.

To make a bodysuit, you first have to get a life cast of an actor's entire torso.

Offscreen: This is the strangest profession there is.

Narrator: Keanu and Alex were covered in purple and green silicone rubbers. The green silicone has an oil in it that ensures it won't pull any of the actors' hairs out of their bodies. The two silicones adhere to each other and are then wrapped in a temporary plaster jacket to hold them together, which will eventually be replaced by a fiberglass shell.

That forms the mold that will shape the bodysuits. The fiberglass torso shell is laid up into the silicone impression, which then gets covered in clay for the sculpting part of the process.

This is the first stage where attention to every realistic detail is crucial, as the team sculpts every muscle and vein onto this mold.

Kevin Yagher: I just wanted to make sure it looked, at every angle, like if he lifted his arm or something, that everything was finished beautifully down here just as much as it was up here.

Narrator: In early design and Photoshop stages, Alex said he actually wanted the muscular Bill to look like a gorilla. Even if the suit's shape is over the top, the basic anatomy can still be convincing. Sculptor Carol Koch kept a model of the human anatomy in front of her as a reference while chipping away at the muscle suits.

Kevin says a common misconception is that when muscles bulge, the veins will too, but veins actually don't get that big.

Kevin: I would have them just keep making those veins subtle, more subtle. So they would just keep smoothing them out until I could barely see them, where they're there, but they didn't look, you know, like if they were worms.

And then when I come back with a painting, that also pops them up, so the combination of a nice sculpture with paint is what makes them look real.

Narrator: Once they've sculpted the shape of the bodysuits with all their details in clay, they make a mold of the clay suit using a thicker silicone, combine the life cast torso shell, and then inject foam latex into it. The outer layer of foam is removed and replaced with a skin-colored layer of silicone.

What about silicone makes it the right material for human skin?

Well, foam wrinkles easily, and silicone can soften those wrinkles. But more importantly, Kevin says, silicone absorbs light the same way human skin does, which goes a long way towards making the suits look real. But it isn't until after the suit is sealed and injected with yet more silicone that Kevin can start to paint details on the skin, as plain foam doesn't look very convincing as an outer skin layer.

The next thing to nail was skin tone. When trying to nail the color palette of the actors' skin, Kevin started with lighter shades to match Keanu and Alex's complexions.

But the prison scene in "Face the Music" was shot in New Orleans during July, when temperatures reached nearly 100 degrees Fahrenheit. And the scene with the muscle suits was shot in a prison yard, so Kevin knew the actors would be spending a lot of time in the sun.

So to compensate, he made the suits a shade darker than their normal skin tone. Or, as Kevin says, he "gave the suits a suntan."

Which gets to an important point. Color makes a big difference in making the skin look real. Take a look at the muscle suits during a nearly completed stage. The abs pop out not just because of how they're sculpted, but because of how they're colored.

The team used an unexpected color combination of red and green paint underneath and around each ab. It's those kinds of surprising details in human skin that only an artist can detect.

Let's go back into that blank area of the muscle suit he colored in with an airbrush. Kevin says there's always some red in a person's skin. So he starts with that red base and then adds shades of green and blue, other colors he's observed in the skin.

Kevin: I use a very tiny, tiny little spray. So, it only maybe puts out, oh, a 16th of an inch a band of color. I do this thing, for some reason I call it wobbly hand, and I just kind of create a kind of wobble, and I also go in and out. So I'm constantly moving my hand like this, and then I'm going in and out, you know, to the thing. It causes little dots; it causes little veins; a little breakup.

Narrator: While that is happening, the left nipple doesn't fully pass until a pinkish-brown coat gets sprayed on it.

The muscle suits were smooth and hairless to mimic bodybuilders, but Keanu's fat suit had hair.

Adding hair to a suit makes it easier to hide skin details, but each hair has to look real, from how it curls to the growth pattern. Kevin punched at least 300 individual hairs into the stomach and chest of Keanu's fake paunch.

He made sure to make the hair thicker and heavier as it went down the chest towards the groin.

Kevin's work isn't only about painting splotches and punching hairs. You can't have a bodysuit that just looks realistic. It also has to move like a real body.

The foam latex beneath the layer of skin-like silicone helps the actors move comfortably. A fat suit, like the one Kevin made for Keanu, needs to bounce and jiggle naturally. You can see that as Keanu's stomach pops out of his shirt during this shot in the film.

So, how do you make it move while also giving it some weight?

The classic technique? Stuffing the suit with dry lentils. Kevin used them when building the suit for Weird Al Yankovic's 1988 music video "Fat."

He later created two body pieces to add 40 pounds to Nicolas Cage in 2002's "Adaptation."

This time around, Kevin tried to achieve movement in one of them by mixing lentils and beads into one of his suits, but the actor's sweat actually caused the lentils to sprout. So now, to get the movement and weight without the mess, Kevin simply fills the chest and stomach of a suit with bags of beads.

Kevin: It kinda jiggles up and down.

Narrator: With all the skill involved in making these suits look and move like real human flesh, some of the realism is achieved by cleverly hiding the dead giveaways.

Makeup artists typically cover up the zippers on the back of bodysuits, but because of that brutal New Orleans heat, they kept the zippers on the muscle suits exposed so the actors could hop in and out of them quickly to cool off. So for a shot like this, the zippers were just CGI'd out.

Kevin also needed to hide the seams where the suit connects to real skin around the neck and the arms. So when wearing the muscle suits, the two actors wore weight-lifting gloves, while Keanu's long fake beard hid the neck seam.

You will also notice Keanu wearing two necklaces in the shots where he has a bigger belly. The lower one was glued down to hide the straps that held the suit up above the chest.

For one final touch of realism, Kevin applied a water and glycerin mix to Keanu and Alex's prison bodysuits to give off a persuasively sweaty look.

All that effort, from punching hundreds of hairs to wearing a 20- to 25-pound suit in punishing heat, created something realistic not just for the viewer, but also the actor.

Kevin: Alex Winter liked to have all that weight, because it helped him in his acting to have enough girth on him to kind of perform better. He was happy with that.