Let's start this off with the correct amount of warning: If you're reading this and haven't seen Captain America: Civil War, then be warned that this article is filled with spoilers.
Sometimes the most enjoyable part of being a comic book geek/fan/nerd/lover is catching subtle hints that point to something from our vast wealth of comic book knowledge within the movies we love so much. Hearing a familiar name while knowing the character's full backstory, or seeing a character or location crop up unexpectedly, inspires us to giggle inside; examples of this are what you'll find below, so be forewarned. These are six of the characters that appear in Captain America: Civil War that actually hold quite a lot of weight in the original comic book story that the movie is based on, although you might not get that from the film.
Spoilers aplenty below, so if you're ready let's get going.
We all probably know by now, with or without having seen the film, that Zemo is the central bad guy. His reaction to the loss of his family (accidentally) during what transpired in Avengers: Age of Ultron is to devastate the Avengers themselves. However, in the comics he holds far more clout, as the name Zemo is attached to more than one man. Firstly, it's associated with Heinrich Zemo, a scientist working for the Nazis, who invented a death ray and had a reddish-pink hood permanently attached to his face thanks to another invention, Adhesive X. He's probably more widely known in the comics for being responsible for trapping our beloved Captain America and positioning Bucky Barnes into becoming the Winter Soldier. Heinrich had a son named Helmut Zemo, who followed in his father's footsteps to become an additional thorn in Cap's side.
2. Maria Stark
If you don't know the name then shame on you, but if you do then you know what an impact she had in the comics. We've seen Howard Stark appear several times in the Marvel Cinematic Universe, yet Captain America: Civil War is the first appearance for his wife, Maria. Up until this point, her name has only ever been an offhand reference or a headline, but in the comics, nearly every hero who has ever been a part of the Avengers has spoken her name. Her importance to the Iron Man mythos is without a doubt more important than the MCU would have you believe, considering that the stock phrase whenever there was collateral damage in the comics was, "Just send the bill to the Maria Stark Foundation."
3. Everett K. Ross
A government official in a Marvel movie usually has a fairly negative role, as we've seen countless times before, yet in Captain America: Civil War we find this government official seemingly undecided as to whether he backs Iron Man or Captain America. He steps into the film as a part of the joint Counter-Terrorism Center, and it'll be interesting to see how the future of the MCU uses his character, considering that in the comics Ross works for the US State Department and is assigned to escort T'Challa while on US soil.
So, he doesn't really play a major role in Captain America: Civil War, but in the comics his name is infamous. He is the man responsible for reprogramming Bucky Barnes and, in essence, creating the Winter Soldier. And what's even more important is the fact that he was involved in a joint operation with Captain America during WWII where he partnered with the Captain and his team against the Red Skull and a supervillain named Master Man.
The MCU introduces King T'Chaka of Wakanda as a glorified means to an end: He is killed as a result of Zemo's treachery, which is blamed on Bucky. This sets in motion T'Chaka's son, T'Challa, to suit up as the Black Panther to avenge his father's death, and goes on to build a great introduction for the solo Black Panther film coming in 2018. Yet, the comics show a much larger role that now T'Chaka cannot fulfill. The comics tell the stories of a time when Captain America and T'Chaka fought side by side during World War II, and he met is demise at the hands of a more devious villain already introduced in Avengers: Age of Ultron: Ulysses Klaw.
If you didn't know the comic version of Redwing, you wouldn't really think anything of it appearing in Captain America: Civil War, yet it was a great reference to the Redwing we know in the comics. The MCU version introduces a drone that accompanies Sam Wilson (a.k.a. Falcon) on several missions, but the comic version is a fairly different, albeit convoluted tale. You'll have to either google it yourself or take my word for it, but here goes: In the comics, Redwing is an actual bird that — through the Red Skull messing with the Cosmic Cube — creates a mental link between Redwing and Sam Wilson. This connection allows them to share thoughts and information, and eventually expands, allowing Falcon to link with other birds as well.