Continuity mistake: When Lex and Clark go to where Lex saw Morgan and it's a bunch of people sewing, Lex grabs a man's hand and puts it on the table. On the table is a piece of fabric that the hands are on, but in the close up shot, there is no fabric. It's back in the next shot.
Other mistake: In the flashback to 1961, "Splendor in the Grass" is playing at the Talon. However, the film was released in October of 1961 and Louise McCallum was killed in June of 1961. So the flashback would be set before the film was released.
Continuity mistake: When Perry arrives at the Kent's, and they start talking, Clark has his hands in his pockets. After being asked it he's a report, Perry starts to walk around and the shot changes and Clark no longer has his hands in his pockets and is then seen putting them in them.
Visible crew/equipment: When Jeremiah has just stabbed Clarke in the barn, after he goes down the steps and the camera follows him walking away you see the back of one crew member's head and then a second crew member's, starting in the bottom right of the screen. Just before scene cuts to black you see the first crew member turn his head to the left. (00:26:46)
Continuity mistake: In the previous episode, "Slumber," Clark wrecks the farm truck by falling asleep while driving. The car has massive damage that, at a minimum, would be extremely expensive and time-consuming to repair. Realistically, though, it is completely totaled. In the episode "Perry," the truck is again in brand new condition, like it was untouched.
Factual error: Clark lifts Chloe's car by the back. He is only holding on to the very back left portion of the car, yet while he's turning it, the car is completely horizontal. The front of the car would buckle since it weighs so much and isn't being handled by its center of gravity.
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