Not every Marvel character gets a sweet guest spot on "Marvel's Agents of S.H.I.E.L.D." coinciding with their birthday, but that's exactly what's happened for Lady Sif! After debuting way back in 1964, the fierce Asgardian will finally make her live action television debut. The character's recent prominence follows decades as a loyal member of Thor's supporting cast, fighting alongside the Thunder God and the Warriors Three across all nine realms – but the Sif we first met 50 years ago made a much different impression upon readers.
Sif debuted 50 years ago in JOURNEY INTO MYSTERY #102, where she played a small role in that issue's "Tales of Asgard" back-up story. Taking place hundreds of years ago when Thor himself was only 18 years old, the Sif found within those few pages bears little resemblance to the fighting female that exists today. In that story, Sif's brother Balder begged Thor to rescue Sif from Hela's clutches.
Thor fights his way into Hela's domain, where he rescues a blonde maiden named Sif by offering up his life in exchange for hers. Hela, surprisingly touched by this offer, released Sif from captivity. Thor didn't know it at the time, but that selfless deed made the young god worthy of lifting Mjolnir for the first time.
The modern Sif didn't make her debut until a few years later.
While fighting the dreaded Unknown with his back up against the wall, Thor nearly succumbed to defeat. Only Sif's intervention and bravado gave him the strength to jump back into the fight.
After defeating the Unknown, Thor recognized Sif from his youth and immediately fell in love with her once more.
Creators Stan Lee and Jack Kirby made a few non-hair color-related tweaks to the character – most notably changing Sif's brother from Balder to Heimdall. This new Sif stood bravely by Thor's side, fighting foe after foe with the warrior's heart that has gone on to define the character. Now, 50 years later, Sif's fighting spirit can be seen in cartoons, movies, and "Marvel's Agents of S.H.I.E.L.D."!