Tempest (1) - S1-E21
Continuity mistake: The way the pillar is on top of Lionel changes in the scene. In the first shot, he's on his side and it lands on his hip. In the next shot he's now on his back and the pillar is going somewhat across his body. In the wide shot of him as the roof falls, the pillar is below his belt, almost perpendicular to his body. Then back to being on his stomach and part of his chest.
Other mistake: Lois digs up Chloe's grave site to unearth her casket. It is obvious that the casket is not buried six feet deep. You would think, with all that is going on, that LuthorCorp would have at least buried the casket deeper to deter inquisitive eyes and maybe throw in a few scattered bones for good measure.
Martha Kent: Clark? What are you still doing out here?
Clark Kent: Well, I'm still doing my chores.
Martha Kent: Well, you usually finish those in about two minutes. How is it that I drove to Metropolis, attended the Children's Foundation dinner, and made it back before you finished?
Clark Kent: Because I'm doing them the normal way.
Question: Throughout the series, people mutate fairly soon after their exposure to kryptonite. Is it ever explained how Lana has managed to wear a piece of kryptonite around her neck for 12 years and not change?
Answer: The kryptonite only creates mutations when it reacts with the environment and an individual. Remember, the FDA and several environmental groups did check out Smallville after the meteor shower, but found no danger in the rocks. Obviously they're not always emitting mutating rays, or all the flora and fauna of the surrounding area would be horribly mutated.
Phoenix