A behind-the-scenes look at 2020's biggest movies

• Even with the COVID-19 pandemic slowing down production, Hollywood managed to put out a slew of exciting new projects full of ambitious stunts and special effects.
• From the massive battle scenes in "Mulan" to the gripping fight sequences in "Birds of Prey,""Extraction," and "The Old Guard," this year's action films pushed actors and stunt performers to undergo extensive weapons and combat training.
• With Pixar's "Onward" and Netflix's "Over the Moon," 3D-animated films found innovative ways to animate and light their characters and worlds, the likes of which we've never seen before.
• Boundary-pushing digital effects made movies like "Dolittle," "Sonic the Hedgehog," and "The Call of the Wild" possible by combining CG animals with live-action humans and environments.

Following is a transcript of the video.

Narrator: 2020 was in many ways a rough year for Hollywood, with the COVID-19 pandemic pushing back some of the year's most anticipated movies. But the industry rallied by releasing no shortage of ambitious and exciting new projects, which brought their own set of breakthroughs in the world of special effects.

From massive battle and fight sequences to some of the most realistic practical effects we've ever seen, here's a behind-the-scenes glimpse at the biggest films of the year. Three, two, one!

To play the legendary warrior Mulan in Disney's live-action film, Liu Yifei spent three months training for up to seven hours a day. This demanding regimen paid off. The film's cinematographer, Mandy Walker, told insider that Yifei was able to execute about 90% of her own stunt work.

In preparation for the film's acrobatic fight sequences, Yifei and her castmates were schooled in everything from weapons handling and archery to military marching and horseback riding. The performers did their most dramatic midair stunts while attached to wires or beams so that it looked like their characters were flying or spinning through the air.

All in all, the film's action sequences required 90 horses, 80 trick riders, 4,000 prop weapons, 281 sets of armor for the Chinese army, and 730 pieces of armor for the Rouran army.

How do you create a terrifying monster out of nothing? It turns out, with a lot of clever camera and stunt work. This scene from "The Invisible Man," where the titular villain throws Elisabeth Moss' character across the table, is actually a bunch of shots stitched together.

First, the crew filmed Elisabeth as she was about to be thrown. Next, they swapped in the actor's stunt double and filmed her being thrown by another stunt performer in a green suit. Then they swapped in Elisabeth again. In postproduction, VFX artists combined the plates, then digitally erased the green-suit performer and the ropes used for the stunt.

For it all to match up perfectly, the crew had to shoot the whole thing with a motion-controlled camera, which could be programmed to perform precise, repeatable camera movements.

That wasn't the only bit of camera trickery in the film. On the last day of shooting, when filming this scene, the camera team had to get what they called "an impossible shot" -- one that involved passing a camera out of a moving car into another moving car, all in one smooth handoff.

"Extraction" marked the directorial debut of Sam Hargrave, the veteran stunt coordinator behind "Atomic Blonde" and a number of Marvel movies. Naturally, then, the Netflix thriller was full of daredevil stunt work -- just as much from the camera crew as from the actors and stunt performers.

The centerpiece of the film was what the crew referred to as "the oner" -- an extended fight scene made to look like one continuous shot. Sam is familiar with big, long action sequences from working on the famous one-shot fight in "Atomic Blonde." But this one for "Extraction" required Sam to take us right into the middle of the action, even strapping himself to the hood of a chase vehicle. Just to get this one smooth shot taking us from outside to inside a car, he had to unstrap himself from that one car, run over to the other vehicle, and then repeat the same shot twice. This is what you call a stitch point, one of the invisible cuts that joined about 36 different segments into what looks like one long, seamless 12-minute take.

For the third installment in the "Bill & Ted" franchise, special effects legend Kevin Yagher created special bodysuits for scenes where Bill and Ted meet future versions of themselves.

The process began with lifecasts of Alex Winter and Keanu Reeves' bodies, which were then used to sculpt the shape of the actors' suits, both the muscle suits they wear in the prison scene and Keanu's fat suit worn in a different scene. Kevin and his team sculpted and spray-painted tiny details like pores and veins onto the muscle suits and added bags of beads into Keanu's fat suit to get just the right jiggle in his belly.

[beads shaking]

The rollout of the "Sonic" movie got off to a rough start when the first trailer was met with backlash from fans who objected to this Sonic's disturbingly realistic appearance. In response, the VFX artists gave the character an overhaul, making his eyes bigger, his mouth more animated, and his nose and limbs more cartoonish, more like the original design in the video games.

Just about everyone liked the redesign better, including the man behind the hedgehog, actor and comedian Ben Schwartz. Ben not only lent his voice to Sonic, but also provided facial motion capture to inform the character's animation. On set, they used different stand-ins for Sonic to give costars like James Marsden something tangible to interact with, whether it was a blue stuffy or just a ball on a tripod.

We saw CGI turn man into hedgehog. What about turning man into dog?

In this year's remake of "The Call of the Wild," veteran motion-capture performer Terry Notary provided an incredible mo-cap performance for the movie's canine protagonist, Buck. Having Terry on set provided a raw-size reference for the other actors and gave costars someone to interact with emotionally.

For Buck's design, the filmmakers used the reference of a real-life shelter dog, whose own name happens to be Buckley. To help guide the animation of the many dog and wolf characters in the film, the team brought in five other dogs for a mo-cap playtime session. But don't worry; no pups were involved in the filming of this scene, where Buck and John Thornton navigate a treacherous river.

The filmmakers enlisted a stuntperson to shoot the real deal on a river in British Columbia. They then combined the on-location shots with blue-screen footage of Harrison Ford paddling on a canoe gimbal, filmed on a motion-controlled camera that allowed for some particularly cinematic, sweeping shots. Finally, VFX artists digitally added Harrison's canine friend into the mix in postproduction.

The character in "Onward" that presented Pixar with the most challenges was this guy, known simply as Dad. He's introduced when Ian, voiced by Tom Holland, carries out a spell to conjure up his late father, but only half of his body appears.

Pixar's animators spent a lot of time on Dad's first scene to make sure it would capture the force and unpredictability of magic. They even took turns blasting each other with a leaf blower to get a feel for what the conjuring effect should look like.

From there, the challenge was giving life to a pair of pants, a task that forced Pixar to bring its cloth technology to a new level. The studio used a process called simulation to program how a character's clothing should respond to his or her movements and the different forces acting on them. But because Dad's upper half is all clothes and no body, simulation played an even bigger role than usual.

To figure out how a person would move if he were missing his top half, Pixar's animators took turns putting on green suits with khakis and moving around in front of a green screen. Later, they digitally removed their top halves and used the footage as reference for what Dad's body language might look like.

"The Call of the Wild" wasn't the only film where CG animals figured prominently. The majority of scenes in "Dolittle" feature live-action humans and CG animals interacting in some way.

The tricky part of that: making sure the humans were looking in the right places during filming. Nailing the eyelines was especially challenging with a character like Betsy the giraffe. To help guide the actors on set, the crew used stuffy props as stand-ins for the CG animals and got creative from there.

Like with Betsy, for instance. They ended up sticking a giraffe head on a long pole, which got driven around on a motor cart. In another scene, Robert Downey Jr. needed to ride the ostrich Plimpton into Buckingham Palace. So they devised a gimballed riding rig that they could later replace with a CG creature, voiced by Kumail Nanjiani.

The action-heavy "Birds of Prey" involved a lot of physical preparation, with each actor's training program tailored to her particular character. Since Harley Quinn is a whimsical and unpredictable fighter, Margot Robbie's stunt work involved a lot of gymnastics.

Black Canary's fighting style was supposed to be more grounded with a lot of legwork, so Jurnee Smollett-Bell's preparation combined tae kwon do and kickboxing. And Mary Elizabeth Winstead adopted judo, jujitsu, and karate to play Huntress, the deadly-accurate assassin who's all about precision.

Early on in Netflix's "Project Power," there's an unforgettable scene where Machine Gun Kelly's character spontaneously bursts into flames. To figure out how to turn MGK into a human fireball, the effects team first set stuntpeople on fire in a series of camera tests.

Then they came up with a breakthrough: an LED suit that would be embedded within layers of burn prosthetics. The LEDs were programmed to illuminate the actor as his character is seen exploding in flames. The gruesome prosthetics helped hide the LED strips, along with all the wires and battery packs.

For MGK, this meant spending five hours in the makeup chair every day of shooting to get hundreds of prosthetic pieces glued on over 95% of his body. The process was so intensive that the rapper started just sleeping in his body prosthetics, and did so for five days straight, even wearing them for a night out on the town with costar Jamie Foxx.

For Netflix's "Jingle Jangle," the biggest challenge was creating a fantastical world where magic and spontaneous musical numbers would feel right at home.

To make Jeronicus fly in this scene, the crew attached Forest Whitaker to wire rigs, later removed in postproduction.

Another particularly fun sequence, the kids' factory escape, was shot in front of a blue screen, with the two young actors rigged to the wooden chest. VFX artists later added in the tunnel and the giant fan and fireball.

In this comic-book adaptation, Charlize Theron's character is supposed to have 6,000 years of martial arts experience, ranging from Greco-Roman wrestling to Filipino stick work. Charlize had to do intense combat training so she could look effortless handling both modern and ancient weapons.

Of course, the star is no stranger to this kind of hardcore training, having done a lot of her own stunts for "Atomic Blonde" and "Mad Max." The "Old Guard" fight coordinator, Danny Hernandez, told Insider that Charlize and Kiki Layne spent four months training for the film's major fight sequence, where their characters engage in epic hand-to-hand combat inside a plane mid-flight.

The payoff? The actors were able to pull off 90% of the fight themselves, without stunt doubles.

How does this shot become this? Through the process of CG lighting, which was especially important to building the magical worlds of Netflix's animated film "Over the Moon."

Creative lighting helped emphasize the dreamy light coming from the moon, which plays a central role in the story. In this shot, the lighting team is perfecting the big, bright moon reflections in Fei Fei's eyes. And in this shot, they're balancing the different light sources coming from the moon, the kitchen, and the colorful lanterns.

These decisions about the intensity and placement of lights are laid out early on in color scripts, which are like artistic blueprints, expressing the mood of any given scene.

For the scenes set on Lunaria, the artists wanted the light to be overpowering and the colors vibrant and bold to give an otherworldly aura to the moon kingdom and invoke a sense of awe in the audience.

The horror movie slash political satire "The Hunt" follows a group of liberals hunting conservatives for sport, so there were lots of opportunities for practical gore behind the scenes.

But the most talked-about sequence was the climactic kitchen fight between Betty Gilpin and Hilary Swank. To make the head-to-head between these two characters feel as messy as possible, the crew designed a special set that was made to be destroyed.

The set included foam floors, a chimney rigged with squibs, and a bunch of household-item breakaway props that were built to be broken, just like this glass window, which shatters in this scene. It was like a twisted jungle gym, meant to serve as the ideal backdrop for all the chaotic violence.

So, did we miss anything? And what do you think were the most impressive effects of 2020?

Let us know in the comments.