December 16 is, in the Marvel Cinematic Universe, a significant date on the calendar. It's the date in 1991 that Bucky Barnes -- then the Winter Soldier and under the control of Hydra -- murdered Tony Stark's parents. It's the reveal of this as well as the fact that Steve Rogers knew and didn't tell Tony about it is one of the biggest twists in Captain America: Civil War. Now, on the 28th anniversary of the tragic deaths of the Starks, many across the Marvel world are taking a moment to acknowledge the odd Marvel fan holiday called Mission Report Day -- including Doctor Strange writer C. Robert Cargill.
On Twitter, Cargill posted honoring Howard Stark noting the fictional anniversary as well as marking things with "#missionreportdecember161991" a nod to what Zemo (Daniel Bruhl) asks Bucky (Sebastian Stan) for numerous times in Civil War, "Mission Report: December16, 1991."
As fans will recall, in Civil War, Zemo spends most of the movie trying to get the information about what went down on that fateful December 16, 1991 mission from Bucky as part of his plan to bring down the Avengers. While it takes Zemo numerous attempts, he is finally successful when Bucky is imprisoned and Zemo poses as a psychiatrist. It's then that he recites the activation words in Russian that turns Bucky back into the mind-controlled killing machine he was when he murdered the Starks.
This ultimately leads to a showdown at the Siberian Hydra base and the revelation that Steve knew that Bucky was responsible for Tony's parents' deaths and didn't tell him. The revelation fractures Tony and Steve's friendship as well as divides the Avengers, a rift that doesn't fully heal until Avengers: Endgame where, after realizing that time travel is possible and could bring back everyone lost when Thanos snapped his fingers in Avengers: Infinity War, Tony comes to aid Steve and the surviving Avengers. He returns to Steve his shield and the pair work together to carry out the Time Heist.
That Time Heist also had another unexpected and deeply moving impact. Tony may never have had the chance to say goodbye to his parents because of a brainwashed Bucky's actions on December 16, 1991, but Endgame gave him a motion of closure with his father, albeit in another part of the timeline, when Tony met a nervous father-to-be Howard Stark and was able to appreciate the father he lost.
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