Agent Carter: 10 Easter Eggs, In-Jokes And References
9. Steve's Blood
Rather than a fun inconsequential reference, the following shows just how inter-connected the Marvel Cinematic Universe really is, even in ways that aren't apparent at first .
In the final episode of the series Valediction, Peggy makes the heart-breaking decision to dispose of the last remaining vial of Steve's blood, rather than have it experimented on so as to rediscover the super soldier serum that gave him his superior strength and stamina. Of course, this symbolised her letting go of Cap and moving on but, if you think about it, this action also explains developments later in the timeline of the MCU.
Thanks to Peggy, the hunt for the super soldier serum had to start again - and never achieved the original's success. This resulted in Project Rebirth from The Incredible Hulk which created both the Hulk and Abomination as well as the Deathlok program, which produced a serum that blends the super soldier formula and the Extremis virus from Iron Man 3, seen in Agents Of SHIELD.