Marvel Cinematic Universe: Definitive Guide To Easter Eggs, In-Jokes And Foreshadowing

Captain America: The First Avenger

8. Bucky Has Been Brainwashed

Although it at first seems like just a way to get Steve Rogers into the battlefield, Bucky's capture by Zola is incredibly important - it's during this time that the Hydra scientist begins his brain-washing of the soldier and makes it so that he can survive that fall. Now that's smart pre-planning.

7. Stan Lee Cameo

Stan Lee didn't start working at Marvel until after the creation of Captain America, making it questionable whether he should appear in The First Avenger (every other hero he'd help create). However, given that he was instrumental in bringing the hero back to join The Avengers in the '60s (and that his cameos are just too much fun), he does make an appearance; he's a military vet who mistakes a military aide for Cap himself.

6. Vibranium Introduction

Captain America's shield marks the MCU debut of vibranium (and distinguishes it from the comics as made of pure metal and not an alloy - Marvel don't have the rights to adamantium). Stark refers to the metal as "vibration absorbent", a property (in the comics at least) distinct to Wakandan vibranium, an early (albeit subtle) nods to Black Panther's home country. Given how Stark describes it as the rarest metal on Earth, however, that suggests he found this elsewhere (possibly the Antarctic).

5. Bucky Holds The Shield

It's a blink-and-you'll-miss-it reference, but moments before his "death", Bucky picks up and briefly uses Captain America's shield. This is some pretty long-term foreshadowing, sowing the seeds of Bucky eventually taking up the Captain America mantle once Steve Rogers dies.