Thoughts on the big (inevitable) Avengers plot twist...

There is really only one genuine plot twist in The Avengers.  Sure there are visual moments that will shock or delight, clever lines of dialogue that one wouldn't want ruined, and/or certain narrative choices that merit discussion.  But there was only one truly 'shocking' moment in the 140-minute picture.  And now I'm going to discuss it.  Right after this first paragraph, so you've got plenty of warning, folks.  If you haven't seen it yet and don't want to know, don't read any further.  I'm giving you plenty of space between the start of this post and the actual discussion of the matter at hand.  SPOILER WARNING staring in  5...4...3...2...1...