When Ash asked for Xylocaine and was told that it was in short supply, he said to use lidocaine instead. Both of those are names for the same local anesthetic,
At 56 min the boy is holding onto a grate leading up from a drainage hatch. As the other two separate the grate outward, the boy's hands release his hold onto the grate, which means he would have fallen back down... but didn't.
During an explosion, the wrinkles in the background of the miniature set can be seen.
At about 32 minutes there's a helicopter flying across the screen. It looks a bit fake, but not bad. The next shot is of the helicopter landing. This time it is definitely a real helicopter, but a completely different kind.