The latest movie from Marvel Studios features a ton of memorable characters, but few anticipated that director Taika Waititi's portrayal of Korg would be as well received as it's been. But the character actually made an appearance before stealing scenes in Thor: Ragnarok, having popped up in the previous film in the God of Thunder's franchise.
In the DVD commentary for Thor: The Dark World, director Alan Taylor revealed the stone-like Kronan that Thor fights in the scenes opening act is actually Korg. But because he was never explicitly named on screen, Waititi and the writers of Thor: Ragnarok were able to retcon the new film into being the character's first appearance.
The character's comic backstory is requires some explanation, given that he wasn't officially named until The Incredible Hulk vol. 2 #93, as part of the "Planet Hulk" storyline. In that comic, he is a fellow prisoner with the Hulk and forced to do battle on Sakaar. The comic retconned his first appearance to tie into the first Marvel comic starring Thor, Journey into Mystery #83.
In Thor's first comic appearance, he appears on Earth and defends the planet from the invading Kronan forces, aka the Stone Men from Saturn. The "Planet Hulk" storyline said that Korg was one of the Kronan's defeated by Thor, and was then imprisoned on Sakaar.
The fact that Korg was first meant to appear in Thor: The Dark World, losing in battle to the God of Thunder, and then retconned to appear in Thor: Ragnarok is very meta. It's almost like Waititi planned it that way from the start.
But it probably more has to do with the inclusion of Bruce Banner and incorporating the "Planet Hulk" storyline into the film, though we wouldn't be surprised of the irony isn't lost on Waititi.
It just goes to show that even though Marvel Studios tries to honor its own continuity, they'll still allow filmmakers to make some changes if it makes for a better movie experience.
Thor: Ragnarok is now playing in theaters everywhere.