An old colleague of Jane Foster's father, Selvig is working with her to carry out her wormhole research, resulting in him being present when Thor arrives on Earth after his banishment. Having grown up with tales of the Viking myths, Selvig recognizes Thor's 'stories', but assumes that they reflect a delusional mental state even after Jane's assistant speculates that the Norse gods could have been an advanced race who came to Earth. However, he and Thor bond after they spend the night drinking in a bar after he helped Thor escape S.H.I.E.L.D. custody.
It is suggested that Selvig also knows Bruce Banner; after SHIELD has taken Jane Foster's equipment, Selvig says that he knew a scientist who was a pioneer in gamma-radiation, but after SHIELD showed up, no one heard from him again. When Lady Sif and the Warriors Three appear outside Jane's lab, Selvig doesn't understand what is going on until the Destroyer appears soon after attacking the town. During the course of the battle, he witnessed the amazing abilities of the Warriors Three and begins to believe Thor's identity. In the midst of the destruction he concedes to following Thor's instructions.
Later in the aftermath of Thor's renewal of his powers and reclamation of his hammer, Selvig no longer doubts Thor's beliefs or identity. Jane and he travel with Thor and the other Asgardians to the wormhole as they depart from Midgard. In a post-credits scene, Selvig meets with Nick Fury and is offered the chance to study the Tesseract, but is already being observed by Loki.
The Avengers
Currently working for S.H.I.E.L.D. investigating the Tesseract, Selvig comes under Loki's control when Loki emerges from the portal generated by the Tesseract. He subsequently helps Loki devise a device that will allow him to generate a larger portal to bring in a massive invasion fleet to conquer Earth. When Loki's plan is about to be fulfilled, Selvig brings the Tesseract to the top of Stark Tower, and uses it to open a portal to the Chitauri's world. When the aliens starts to spawn on Earth, Selvig is reached by the Avengers, who try to stop him and fail. Selvig reveals to them that the force field surrounding the Cube is unbreakable, and that nothing can be undone. He is knocked out by the force of the portal immediately after.
When he wakes up, Selvig finds himself alone with the Black Widow, who's trying to close the portal. Back to himself, Erik reveals to her that some part of his consciousness was still awake during Loki's mind-control, and that he inserted a flaw in the god's plan: the force field around the Tesseract can be undone with Loki's scepter. He is last seen standing with the Avengers as Thor takes Loki and the Tesseract back to Asgard.
