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Chosen answer: While not explicitly spelled out in the films to date, it's implied that Howard Stark developed the arc reactor technology after extensive study of the Tesseract that he retrieved from the ocean floor at the end of the movie. As such, Hydra's Tesseract-powered weaponry and the arc reactor-powered systems in the Iron Man suits share something of a common origin, hence the similar sound.

Tailkinker ★

Chosen answer: A couple of techniques were used. In most cases, Evans would film the scene normally, then the effects team would digitally shrink his character down to the smaller size. This would generally require some on-set adjustment to allow for eyelines - in some cases Evans would be physically lower than other actors, in others, they would look at his upper chest while he looked over their heads. In a few cases, actor Leander Deeny, who possessed the necessary scrawny physique, would film the scene, collaborating closely with Evans to ensure that the character's mannerisms remained the same. Deeny's features would then be digitally replaced with those of Chris Evans. Deeny appears briefly in the movie as the bartender in the pub Rogers visits to recruit his team.

Tailkinker ★