Here's a Secret...
... People wake up during surgery ALL THE TIME. Well, when I say 'wake up' I don't mean they sit up and start chatting with the surgeon about last week's episode of Survivor... but more awake you'd think.
I don't remember when the first time I saw it was, but I guess it was back when I was a med student. If you're not warned beforehand and the patient suddenly starts bucking, it is a truly scary thing. At the time, what shocked me even more was how nonchalant everyone was about it. The surgeon calmly called the anesthesiologist's attention to the fact that the patient 'was a little light'. This wasn't readily apparent to the anesthesiologist because once the patient is asleep they are likely to be napping, reading a book, doing a crossword puzzle, checking their e-mail, talking on the phone, or, in one of my most bizarre OR experiences to date, constructing an elaborate tent out of sterile drapes and towel clips to shield themselves from a draft.
So the anesthesiologist, alerted to the fact that their patient seems to be two seconds away from taking the scalpel from the surgeons hand and circumcising him with it, calmly drew up a little more rocuronium (paralytic) and injected it. Crazy. Now usually, there would be signs that the patient was not as deeply under anesthetic as he should be... in response to pain, even unconscious people will show an increased heart rate and blood pressure. Usually, the anesthesiologist will pick up on that and top them up, either with stinky gas or with the good stuff (fentanyl, sufentanil). I'm not sure why this time was different. I have a hypothesis though... see my previous post on medical errors.
Luckily, even if the patient DID wake up in the middle of surgery they'd never remember it. The main drug used in anesthesia (the one that actually puts you to sleep most of the time) not only puts you under, but is a pretty potent amnestic agent. (Insert evil laugh here)
So good luck the next time you have to go in for surgery.