It goes without saying that the obvious stars of the Marvel Cinematic Universe are the main characters - Robert Downey Jr's Tony Stark, Chris Hemsworth's Thor, Tom Hiddleston's Loki and Chris Evans' Captain America, for example. However, some of the lesser characters have also been very interesting to watch. Sadly, some of these characters have been limited to one movie or live action appearance so far. In this article, we'll be looking at some of the best non-essential characters who have only appeared in live action once, but whose return would be welcome (and by "non-essential", I simply mean that it wouldn't really make any difference to the progression of the Marvel Cinematic Universe, in the grand scheme of things, if they didn't appear again). On that note, here are ten non-essential Marvel Cinematic Universe characters who we've only seen once, but we'd like to see again (note, this will not take in to consideration any appearances in the tie-in comics, only live action appearances)...