The Avengers Bits you missed/ can't remember/ couldn't hear

[Dark Raven]

Quite a few noticed back when the movie came out. As for the how? Back around when the movie came out there were some interviews with Tom (some if may have been from set interview stuff) where he mentions that, before filming began, he and Joss sat down and talked about the backstory of what had happened to Loki between letting go at the end of Thor and when we first see him in Avengers. Tom breaks it down simply saying that, during that year between films, that Loki's "sort of been to the seventh circle of hell and back"

Spoiler

If they bring him back to life in Avengers 4, they can say that it was as a result of his murder in Infinity War. It could be that his past self is already experiencing the effects of something that would only happen to him later in the future. It could be some sort of temporal loop.