A pilot, written by Joss Whedon, Jed Whedon, and Maurissa Tancharoen, and directed by Joss Whedon, was given the green light in late 2012 and filmed in early 2013. The series was officially ordered on May 10, 2013 and premiered on September 24, 2013. On October 10, 2013, ABC picked it up for a full season of 22 episodes.
Agent Phil Coulson puts together a small team of S.H.I.E.L.D. agents to handle strange new cases. Each case will test the team in cooperation and ingenuity as they try to work together in trying to save the world from threatening, supernatural events on Earth.
Clark Gregg as Phil Coulson: The character headlines the series. Coulson is a S.H.I.E.L.D. agent who oversees many of the division's field operations. Though he appeared to have died at the hands of Loki in The Avengers, he is revealed in the series pilot to have been revived by medical technicians after having been clinically dead for eight seconds. Speaking of his character's return from the dead, Gregg said, "When Joss described to me the mystery... and the complexity and the unanswered questions about Phil Coulson standing there trying to deal with this, I found it so fascinating and so true to the world of the comics and mythology in general as I understand them that I was immediately in." The changes that Coulson has undergone since his survival from a near death experience will be explored during the first season. Executive producer Jeffrey Bell explains, "There is a lot that's strange and different about Coulson since his return to duty, and even he's noticing it. It sets him on a quest. 'What happened to me? Why am I feeling this way? Who am I?". Executive producer Jeph Loeb adds that Coulson may regret uncovering his answers saying "When you start to pull on a thread, you run the risk of unraveling the whole sweater." Coulson's return has led many fans to theorize that he is a Life Model Decoy, a S.H.I.E.L.D. - designed robot that in the comics, duplicates all outward aspects of a living person. Coulson is revealed to have been revived days he died, and not mere minutes, in the episode "The Magical Place". The specific reason for Director Fury reviving Coulson has not been revealed yet.
Ming-Na Wen as Melinda May: A S.H.I.E.L.D ace pilot and weapons expert, whose nickname is "the Cavalry", although she dislikes the name, as the events that led to its coining during her time as a field agent haunt her, having left her "very quiet and a little damaged". The experience was so horrific that she took an obscure desk job before Coulson recruits her in the series pilot. According to Wen, May "needed to be saved. She returned to S.H.I.E.L.D. out of loyalty to Coulson, but there's a part of her that remains reluctant. She still gets her pissed-off face. If it weren't for his intervention, she'd still be down in that dark, dingy room stapling things." The character was originally listed with the name Agent Althea Rice on casting sheets.
Brett Dalton as Grant Ward: A S.H.I.E.L.D. black ops specialist. He is a gruff, unsociable "manly man" in his early 30's who is great at his job, but not so great at getting along with his coworkers. Ward has a strong moral foundation and is not without his charm.
Chloe Bennet as Skye: A civilian recruit who is a computer hacker and member of the hacktivist group called "the Rising Tide." Skye is described as "bubbly and goofy" but "also warm, edgy and witty". She can more than hold her own in any situation. Skye is obsessed with superheroes. In "The Girl with the Flower Dress," it is revealed that Skye joined S.H.I.E.L.D. and Rising Tide in order to find out about her parents.
Iain De Caestecker as Leo Fitz: An agent of S.H.I.E.L.D. who specializes in engineering, especially weapons technology. De Caestacker downplays the apparent romantic chemistry between Fitz and Simmons, insisting that Simmons is merely "motherly" toward Fitz.
Elizabeth Henstridge as Jemma Simmons: An agent of S.H.I.E.L.D. who specializes in life sciences (both human and alien). She is generally cheerful and enthusiastic about her work. Agents Fitz and Simmons are close partners. Henstridge believes that Fitz and Simmons "do love each other but would never, ever say it."