Agent Carter was the second TV spin-off of the Marvel Cinematic Universe and was meant to build the bridge between several past and present MCU storylines. Set in 1946 after the events of Captain America: The First Avenger, the series follows SSR agent Peggy Carter as she works alongside Howard Stark and the Jarvis family to build a new intelligence agency that would later be known as S.H.I.E.L.D. Despite a strong fanbase and positive reviews, the series only lasted two seasons and was canceled in 2016.
Peggy's actions in Agent Carter had a powerful, though subtle, influence on the MCU. Her friendship with Howard Stark literally saved his life at one point — an action that ensured the birth of Tony Stark/Iron Man. She also influenced the scientific achievements of Bruce Banner in Season 1, when she destroys the last remaining sample of Steve Roger's blood so that no one could ever use it again, sacrificing the last piece of him for the greater good. This action has a direct impact on Banner who would later become the Hulk after trying to replicate the Super Soldier serum. If Peggy hadn't destroyed the sample, Banner would have never become the Hulk.
Though clearly deeply connected to the MCU, Agent Carter ended after only two seasons due to network changes and poor viewership. After the mediocre numbers of Season 1, the series couldn't survive the estimated drop of over 2 million viewers in its second season. Another issue was a change at the ABC network when president Paul Lee stepped down. Lee had a scheduling method that would air series of similar genres in the timeslot of more popular shows while they were on hiatus with Agent Carter, serving as the fill-in for Agents of S.H.I.E.L.D. Lee's replacement, Channing Dungey, did away with this method, making the already failing Agent Carter completely redundant in the eyes of the network.
Actress Hayley Atwell further explained the cancelation in an interview with The AV Club. "It's a shame the network canceled it and wanted to put me in something more mainstream," she said. "You know, Marvel didn't want it to end. There's lots of online campaigns to bring her back. Fans loved her. I think it was just a network economical thing: 'Let's put Hayley Atwell in something more mainstream that's less genre-specific and see if we can get higher ratings'. And unfortunately, that isn't, as an actor, anything I've got control over." The "mainstream" project that Atwell refers to was the legal drama Conviction, which was also prematurely canceled thanks to poor viewership.
Fans of the series have not forgotten the series, and have been pushing for Peggy's return on Disney+. Even Marvel TV boss Jeph Loeb is on board. At a Reddit AMA, Loeb wrote excitedly about a possible revival. "Wouldn't that be cool?" he said. "Find us a network! Hayley has been kind of saying she'd love to come back."
Atwell herself has expressed interest in bringing the series back, but didn't deny that she'd be picky about who picked it up and when. "I think the main thing, though, is if it were – if there were interest in Netflix or in her being in a film or something – that it would have to feel... it would have to feel right," she said at a Comic-Con panel in Seattle in 2018. "If she's had an impact on audiences, let that impact grow, so it delights them, but I think it should be to do with more of the current climate now. What are smart issues to bring up? How to create any sort of kind of social weight, an emotional kind of gravitas to the show."
No matter the cancelation of her solo series, Agent Carter continues to live on in the hearts of Marvel fans. She was last seen in Avengers: Endgame, finally reunited with Steve Rogers, and got her happy ending.