Funny enough, the first Avenger was the last of the big three (including Iron Man and Thor) to kick off his standalone movies. Captain America: The First Avenger formerly introduces Steve Rogers and his super-soldier serum charged muscles to the MCU, along with a slew of other pivotal characters.
On the other side of the lens, Captain America's first movie also debuts the writing talents of Christopher Markus and Stephen McFeely, the screenwriters who would go on to helm the iconic Infinity War and Endgame. Their fantastic script expertly balances many an important character, and while screen time is certainly not equal, the time they do have in this film goes a long way in establishing and setting some of them up for future appearances.
Falsworth & Dum Dum Dugan (~9:40)
Both members of Captain America's Howling Commandos, James Montgomery Falsworth and Timothy "Dum Dum" Dugan make their first appearances in the POW (prisoner of war) cells of a HYDRA base.
After being recruited by Captain America himself, the two of them (along with the rest of the Commandos) bring the fight right to HYDRA, destroying their bases and crippling their vast operations. Their loyalty is shown beyond the war when they solemnly toast to Captain America's sacrifice in the midst of victory celebrations. Even though these events take place long before the contemporary timeline, Dum Dum Dugan can still be found in other MCU projects.
Howard Stark (~10:12)
A man whose influence and legacy goes well beyond the scope of this film, Howard Stark's younger days are given a glimpse in the first Captain America standalone flick. First appearing at the 1943 World Exposition of Tomorrow, Stark showcases a genius working out the kinks of his technology, while still managing to captivate his audience's imagination.
He's later brought onto Project Rebirth, helping Captain America gear up for the battlefield. From being in the room for Steve's serum injections to granting him the fabled shield and rediscovering the Tesseract, Stark is present for countless key moments in the MCU.
Jones (~10:17)
The Howling Commandos are represented once again with the quick-witted and multilingual Gabe Jones. Jones is first seen in the POW cells of a HYDRA base with the rest of the future Howling Commandos.
During their escape, Jones commandeers a HYDRA tank along with Dum Dum Dugan and Falsworth, wreaking havoc and ultimately bringing it back with them to the American camp. While most of his screen time is shared with the rest of the Commandos, he gets some solo time to shine during the mission to capture Dr. Arnim Zola.
Dr. Arnim Zola (~15:19)
Debuting in his human form, persevering HYDRA scientist Dr. Arnim Zola first appears as the right-hand man to HYDRA leader, Johann Schmidt (Red Skull). At Schmidt's direction, Zola successfully manages to extract and harness the pure energy of the Tesseract, eventually weaponizing it in the form of HYDRA's tanks and guns.
His position at Red Skull's side and his knowledge of their futuristic technology made him a valuable asset to the Americans once he was captured by the Howling Commandos. However, bringing him to their side would prove to have grave consequences.
Dr. Abraham Erskine (~16:07)
The father of super-soldiers himself, Dr. Abraham Erskine meets Steve Rogers at the start of his journey (and the end of his own). After observing his earnestness, he brings Steve in as a candidate for Project Rebirth, where he eventually proves his worthiness.
Having perfected his serum since he was forced to administer it to Johann Schmidt, he successfully grants Steve the same power, only to be assassinated shortly after, unable to witness Steve's rise to the mantle of Captain America. But as evidenced in the recent hit, Falcon and The Winter Soldier, his work and its repercussions would far outlive him.
Bucky Barnes (~17:52)
The man that broke up the Avengers had a relatively underwhelming debut. Coming to Steve's rescue in the back alley of a movie theater, Bucky first appears in his army uniform having just been drafted to the 107th (Steve's father's old infantry).
After leaving him at the World Exposition of Tomorrow, the two life-long friends aren't reunited until a post-serum Steve comes to his rescue at the HYDRA base. On the mission to capture Arnim Zola, Bucky falls to his presumed death, with Steve as a witness. But of course, that was just the beginning of Bucky's perilous journey.
Colonel Phillips (~21:10)
One of the last to get on board with Captain America, Colonel Chester Phillips expressed his doubts about Steve from the start. Even after a newly muscled Steve literally ran down Dr. Erskine's assassin, he still kept him on the sidelines, opting to hand him over for study instead of sending him to the battlefield.
But even Phillips couldn't deny him after Steve singlehandedly freed the POWs from the HYDRA base, bringing HYDRA technology and information on their whereabouts back with him. In their pursuit of Red Skull, Phillips takes the wheel and ensures Captain America gets on Red Skull's escaping plane in the knick of time.
Red Skull/Johann Schmidt (~27:34)
The big bad of this film (and future gatekeeper of the Soul Stone), Johann Schmidt broke away from Hitler and the Nazis in pursuit of his own maniacal goal. Schmidt first appears in Tonsberg, Norway, where he tracks down and obtains the mythical Tesseract before ordering the complete annihilation of the town.
With the power of the Tesseract under his control, he cuts all ties with the Nazis and establishes HYDRA as a world threat of its own. While Captain America foils his plans, it is Red Skull's own hubris that seals his fate, with the power of the Tesseract casting him out into space.
Agent Peggy Carter (~36:14)
Future co-founder of S.H.I.E.L.D., Agent Peggy Carter's first appearance is a memorable one, highlighted by a strong right hook to the face of an obnoxious soldier. A key member of Project Rebirth, she's with Dr. Erskine and Colonel Phillips every step of the way, getting a front-row seat to Steve's momentous transformation.
Following the assassination of Erskine, she showcases her deadeye accuracy by taking out the assailant at the wheel of the getaway car with a single shot from her pistol. In a cruel twist of fate, she's forced to say goodbye to Steve shortly after their first kiss, granting him a raincheck on their dance as he plunges to his presumed death.
Captain America/Steve Rogers (~1:24:41)
With his name in the title, it's only fitting that Steve Rogers (AKA the original Captain America) dominates when it comes to screen time. Viewers are first introduced to Rogers as a scrawny but eager guy trying to enlist for World War II, only to be emphatically denied time and again, with recruiters citing his endless list of ailments as the reason.
But with the belief and support of Dr. Erskine, his body is transformed to match the size of his heart. Captain America sacrifices his time with Peggy for the good of the world, before being revived in a new era that still needs his heroic services.