If they had left Bucky completely out of the upcoming Marvel movie "The First Avenger: Captain America," I would not have been remotely surprised.
After all, Chris Nolan made the decision to completely ignore Robin in his modern take on Batman, convinced that there's no way to do it without people snickering, and sidestepping the issue altogether certainly hasn't hurt the way people view the Batman movies.
So if they had made this film without ever once referencing Bucky, it would have been one of those major creative adjustments that I would have understood. Wouldn't necessarily be the choice I would make, but I would understand it. It's hard to sell the idea of the underage sidekick for a superhero. There's just too much pop culture that's made fun of the idea so mercilessly.
So hats off to Marvel for casting Sebastian Stan as Bucky Barnes, who was too young to join the Army but old enough to suit up and fight alongside Captain America, and whose fate at the hands of the Red Skull marked a major turning point for many comic readers. In recent years, new narrative choices have expanded the role of Bucky in the Marvel Universe, and word is Stan's signed for as many as six movies.