Some of my favorite moments are when the protagonist(s) wake up and realize they are in a horrible situation.
Check out the first couple of minutes of the Amazon ALPHA HOUSE pilot, which I was not able to post. (No clip on YouTube, but Amazon Prime members stream this Garry Trudeau-created series starring John Goodman for free.)
Anyway, here are a few of the "Waking Up To a Startling Realization" bits from some movies. These are all great moments, even if you don't know the context. But I think all of us have seen these by now. There must be a lot more of these moments ....
Like I said, some of these are NSFW. Especially this first one.
FOUR WEDDINGS AND A FUNERAL
PLANES TRAINS AND AUTOMOBILES