Marvel Studios is once again earning accolades for their de-aging technology in Ant-Man & the Wasp. Surprisingly, though, the studio's best CGI was still years ago - when they created a fake Robert Downey Jr. in Iron Man 3, without anyone even noticing it.

Over the last few years, Marvel Studios has gained a reputation for cleverly manipulating actors' faces to look younger, using a combination of make-up and digital trickery. They started playing with this technology back in Captain America: The Winter Soldier, when CGI was used to digitally age Hayley Atwell's Peggy Carter. Ant-Man had Michael Douglas play a young Hank Pym, Captain America: Civil War had scenes using a 1980s-era Robert Downey Jr., and Guardians of the Galaxy Vol. 2 featured Kurt Russell as a young version of Ego. Ant-Man & the Wasp has done it again, rejuvenating Douglas's Hank Pym (again), along with Michelle Pfeiffer's Janet Van Dyne.

Related: 17 Actors Made Younger With Crazy CGI

But forget deaging. As flashy and exciting as that may be, the real test of good visual effects is when the audience doesn't even realize what they're seeing is fake. And during the making of Iron Man 3, an on-set injury forced Marvel to get creative and film some of Robert Downey Jr.'s scenes using a body double, who was later digitally manipulated to look like the real thing.

Why There Was A Fake Robert Downey Jr. in Iron Man 3

Iron Man 3 Robert Downey Jr Tony Stark

In 2012, production on Iron Man 3 was delayed when Downey sustained on injury on set. The actor sprained his ankle, which posed a problem for some of the action sequences - and Iron Man 3's script notably featured a lot of scenes in which Stark wasn't wearing his trademark armor. Production was stalled for a full six weeks, and Marvel faced some difficult choices. They could potentially push back the film's release date - or, alternatively, they could get creative. This being Marvel, the VFX team chose to do the latter.

In an interview with IGN, VFX supervisor Chris Townsend explained that Marvel used a body double to film the scenes. "We were able to reconstruct RDJ as Tony Stark on set," he revealed, "with the help of [a] body double and the facial captures we'd collected afterwards." It was an innovative technique, similar to the one Marvel had used back in 2011 to put Chris Evans' face on a young Steve Rogers. It's possible that the same approach was used for Avengers: Infinity War, where a number of scenes were filmed with a body double for Benedict Cumberbatch, whose schedule clashed with the movie's production dates.

The most remarkable thing about Iron Man 3's digital make-up, of course, is that it's invisible. Nobody would actually notice that some of the key scenes - such as the entire scene at the end of the film, when Tony throws his old reactor into the ocean - were actually created using a body double and VFX. Deaging is drawing attention because it's noticeable, since viewers are aware the actors aren't really that young anymore. But creating a perfect duplicate of a living actor, to the extent that viewers wouldn't even realize he wasn't on-set at the time of filming, is a step beyond that.

More: Marvel Has Perfected CGI Deaging - Here Are The Movies They Should Make

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