- Crossbones recalls how Bucky remembered Steve after the reveal of his identity in Captain America: The Winter Soldier, though he mixes up or lies about some of the details to mock Steve.
- The HYDRA brainwashing method used to keep the Winter Soldier obedient is the Faustus technique that debuted in and was a plot point in the second season of Agents of S.H.I.E.L.D.. ("Are you ready to comply?"/"Ready to comply.") The technique was developed by Johann Fennhoff, who was the main villain of the first season of Agent Carter.
- Bucky's Trigger Phrase is loaded with nods to various things in the MCU: "One", "Nine", and "Seventeen" references the fact that MCU Bucky was born in 1917. "Freight car" calls back to his falling from the train in Captain America: The First Avenger, while "Homecoming" is a nod to the (then upcoming) Spider-Man: Homecoming film.
- Just like in The Winter Soldier, Steve's fight against a Brainwashed and Crazy Bucky ends with the two plummeting into a body of water. This time, however, it's Steve who pulls Bucky from the water to save his life.
- Tony recalls an incident where Pepper was almost killed and Tony ended up blowing up all his suits.
- Bruce Banner and Thor are still missing after the events of Age of Ultron. Ross even uses this to criticize the Avengers, saying that he'd be chastised heavily if he lost a pair of WMDs.
- When Scott Lang shows up, he and Sam have a brief conversation about what happened during their first meeting. Sam even warns him that it won't happen again.
- Ant-Man shrinks down to damage an armored foe's suit from the inside, just as he did with the Falcon's jetpack in his own movie, or Cross's Yellowjacket suit. (He doesn't have to risk himself by going subatomic this time.)
- Scott later tells Tony that Hank Pym was right to have warned him against ever getting involved with the Starks.
- Back to Cap's first movie:
- The "Where are you from?" exchange between Captain America and Spider-Man ends up nearly quoting the similar exchange between Steve Rogers and Doctor Erskine. Like Erskine, Spider-Man hails from Queens.
- Likewise to Iron Man's first movie: during a fight, Iron Man's targeting systems are knocked out when he has to shoot a missile, so he decides to aim it by sight. During his final fight with Obadiah Stane, Tony knocks out his armor's targeting system, forcing Stane to try to aim missiles himself. Where Stane misses repeatedly, Tony nails his target in one shot.
- Vision mentions that powerful adversaries have only been popping up in the years since Tony announced that he was Iron Man. In-universe this is incorrect (just ask Red Skull or the Frost Giants) but out-of-universe it is right on the money.
- Howard Stark recognizes "Sergeant Barnes" before he kills him and his wife.
- Like in Captain America: The First Avenger, Steve and Bucky have a brief moment reminiscing about going to a fair in their youth, before they enter a bad guy's hideout (the train in First Avenger vs. the Siberian HYDRA base in Civil War.)
- In Captain America: The Winter Soldier, Black Widow tells Steve that The Winter Soldier once shot her and she still has the bullet wound scar. In this movie, when re-brainwashed Bucky fights Widow, Tony, and T'Challa after escaping confinement, she tells him "you could at least recognize me!"
- Sam dodges an attack by retracting his wings, shutting off his engines, and tucking himself into a ball to quickly lose altitude, as he did against an Insight quinjet in Captain America: The Winter Soldier.
- Also from Winter Soldier, the Running Gag of Cap jacking cars makes a return in the tunnel chase scene.
- The news ticker mentions a few events from Agents of S.H.I.E.L.D., such as the ATCU (Advanced Threat Containment Unit).
- During the final fight when Tony's employing the countermeasures against Steve, Tony utilizes his repulsors to increase the force of his backhand hits to Steve's face. Tony employed the same strategy in his fight against Killian in Iron Man 3.
- War Machine's armor has a bunch of tiny Ultron heads on it, for his kills during the climax of Age of Ultron.
- Both Tony and War Machine use sonic weapons, much like Ross did in The Incredible Hulk. And those may have been based on Stane's device way back in Iron Man.
- A retroactive one: After Spider-Man catches Captain America's shield, Tony says "Nice job, kid!". He previously said "Nice work, kid!" to a little Iron Man cosplayer in Iron Man 2. And Word of God eventually confirmed that kid was little Peter Parker!
- Remember the climax of Iron Man, when Stane couldn't hit the broad side of a barn in his Iron Monger suit with the disabled targeting? Tony runs into the same problem trying to murder Bucky, and wisely decides to spend his missile on a much larger target; the hatch of the abandoned silo they're in, so Bucky can't get away. He may even have remembered what happened when Stane tried to kill him.
Continuity Nod / Captain America: Civil War