Continuity Is (Not) Important
A few years ago I did some union extra work on a film that went nowhere. Being an extra is horrible- it's like being glorified scenery. You sit around for hours on end and usually you are paired with someone really annoying who thinks this is "acting". I had that same experience when I was on the set of this particular movie, but the money was so good and I needed it at the time, so I did it.
It was two days of this restaurant scene, and the theme was the restaurant was one of those "eat in the dark" places, and it was shot "night vision style" hence the green hue. At any moment I expected Buffalo Bill from Silence of the Lambs to pounce out with his magnificent tuck job, but that's besides the point.
Months after shooting wrapped, I got a call- they wanted to re-shoot the ending of the restaurant scene, and was I available tomorrow? Well, seeing as how I'm not a contracted actor, unless you pay me a lot more, no. I really really did not want to end up back in that room for another day so they could re-shoot a scene that I'm sure was no better than the first. So they found a replacement actress, and spliced it together.