Captain America: Civil War is finally here!

Avengers: Age of Ultron may not have been the ultimate sequel that fans were hoping for, but many believe that Civil War will get the Marvel Cinematic Universe back on track. Somehow, the film assembles a huge cast of characters and juggles a number of different storylines without anything feeling extraneous or unnecessary.

Of course, with so many different heroes on-screen at once, references and Easter eggs were all but inevitable. Marvel movies have always featured nods to the original works, and Civil War is no different — in fact, it may have more subtle references back to the comics than any other movie in the company's library.

Granted, going over each and every little reference would take forever — instead, we'll be focusing on the biggest and best of the lot. Marvel did a great job of adapting a huge story from the comic books and making it work on the big screen, and these sly nods and Easter eggs only add to the experience.

SPOILER WARNING:

It's almost impossible to avoid spoilers when talking about some of these references, so if you haven't seen the movie yet, bookmark this page and come back when you have!

Bird vs. Machine

It's not all that uncommon for directors and producers to sneak their way into movies (just look at the dozens of different Stan Lee cameos), but co-director Joe Russo has a much darker cameo in Civil War than that of his peers.

In the second half of the movie, the audience learns that the Helmut Zemo killed and replaced Bucky's original doctor in order to gain access to the Winter Soldier's cell. The only time fans ever get a look at the real doctor is when he's found dead in a Berlin hotel room — and yes, that is Joe Russo doing an amazing job as a dead body dumped in a bathtub.

This isn't the first time Russo has had a cameo in a Captain America movie, either: in The Winter Soldier (pictured above), Russo played one of the doctors attending to Nick Fury after the latter faked his death. Let's just hope that Russo's inevitable Avengers: Infinity War appearance isn't quite so morbid as his latest cameo ...

Of course, these references and Easter eggs only scratch the surface of what Marvel was able to hide away in Civil War — let us know which nod to the comics was your favorite in the comments below!

Captain America: Civil War hits theaters on May 6.