I just submitted a review for X-men - the last stand. By the time I had automatically been jumped to my pending page, the review had already disappeared onto the rejects pile.
This has to be the fastest turnround of a review, ever.
Well, I had something like that too. I had a review for MI which was rejected, I changed it a bit and resubmitted it and BOOM it was accepted. That's even more amazing to me since when I re-submit it always seems to take longer for the MERPs to get to those than first submission reviews.
I've had a review drop instantly into the reject pile because it was an exact replica of an existing review I hadn't spotted. Like Benj said - that's probably your answer.
As for fast turnarounds, when the MERPs did that big clean out a few weeks back I submitted a review for The Matrix Reloaded that instantly got approved, so I went and wrote a quick Matrix Revolutions one, and that got instantly approved as well, earning me two completed accolades in under two minutes. I had the feeling if I could keep thinking of approvable reviews and sat there all night I could get my ranking right up. As it was I had to sleep.