Check out this deleted scene from The Avengers that will be included on the Blu-ray set (on sale September 25). In the clip, Bruce Banner (Mark Ruffalo) talks to the security guard (Harry Dean Stanton) after Hulking-out, and it sounds like he's still unsure about his being the Hulk -
Guard: "Which one is it?"
Guard: "Are you a big guy that gets all little, or a little guy that sometimes blows up large?"
Banner: "You know, I'm not even sure."
UPDATE: 8/21/12 - The YouTube clip has been removed, so visit Entertainment Weekly to view the scene mentioned above.
Thanks to EW, CBM, and @movie_maniac_