Marvel Cinematic Universe: Definitive Guide To Easter Eggs, In-Jokes And Foreshadowing
Captain America: The Winter Soldier
16. Senator Stern Again
After a strange cameo in Iron Man 2, Garry Shandling's Senator Stern returns again in The Winter Soldier, revealed to be an undercover member of Hydra, lending a whole new light to his hard work to get ahold of Tony Stark's armour in the earlier film.
15. Moon Knight Nod
When Agent Sitwell reveals some of the persons of interest that Zola's algorithm has targeted he manages to namecheck several of the Marvel Universe's big hitters. On top of Bruce Banner (who's obviously already appeared), there's references to previously unseen heroes setting up later screen debuts. The first person Jasper mentions is "a TV anchor in Cairo", quite likely Marc Spector, who became Moon Knight in Egypt. Moon Knight has no set future appearance on screen, but, with the MCU expanding at an astronomical rate, it's only a matter of time.
14. Doctor Strange Introduction
Bigger than Moon Knight is the first proper mention (after one of his signature objects was glimpsed in Thor) of Stephen Strange. Nothing beyond his existence is given away, although it does reveal that the Sorcerer Supreme is already established in the MCU, setting the stage for a very mystical experience when his stand-alone movie hits in 2016.
13. Winter Soldiers Mask Is A Reverse Of Cap's
In the comics, Bucky sports a simple eye mask, but the film version gives him one that covers the entire underside of his face. Ostensibly to hide his identity ahead of the Wikipedia-spoiler reveal, this also doubles up as a nice little visual cue; it's an exact reverse of Captain America's. An early nod towards his relationship to Steve, it will go on to serve as a nice visual summation of Bucky's character arc; he will eventually take up the Captain America mantle.
12. Bucky Holds The Shield (Again)
If the mask was too subtle, here's another nod to Bucky's future as Cap; similar to the first movie, there's a brief shot of him holding the shield during his street fight with Captain America.