In an eminently gif-able moment in Captain America: The First Avenger, Steve Rogers (Chris Evans) first emerges as a super soldier and Peggy Carter (Hayley Atwell) does what any self-respecting human being would do: She reaches out and touches his pec.
Well it turns out that moment was improvised by Atwell, who was so taken aback by seeing Evans shirtless for the first time that she “impulsively grabbed his boob.” While she's shared the story with Esquire before, you can hear her tell it herself (and pull some funny faces) at a recent Comic Con in St. Louis: