Bruce Banner

Bruce Banner (also known as the hulk) is a character in the Marvel Cinematic Universe and a friend of Thor Odinson's and close to Valkyrie.

Thor (2011)
Erik Selvig mentions a friend of his being exposed by Gamma radiation and SHIELD's involvement with him, never being heard from again, an early reference to Bruce Banner.

Thor: The Dark World
Banner is indirectly mentioned by Loki. He says that since Thor is not comfortable with Loki's presence, he will transform into "one of his companions," since he likes them so much.