Other mistake: When Jimmy wakes up in 1940, on his desk calendar it's Saturday the 3rd. The newspaper says it's May 3rd, 1940, but that was a Friday.
Other mistake: Jonathan Kent's headstone says he was born September 1, 1954. However, in "Relic", we learn Jor-El visited Smallville in 1961, where he met Jonathan's parents and his mom was pregnant with Jonathan. And we know it was him since Hiram (his dad) wanted to name their son Gene and Jessica corrects him and says his name is going to be Jonathan. Plus, if he was born in 1954, he would have been 25 when he won the high school state championship instead of a more realistic 18 if he was born in 1961.
Other mistake: The bowling scorecard for Chloe and Lana is wrong. It shows Chloe knocking down 1 pin (-|1) in the first frame but getting 3 points, then a spare in the 2nd frame but only getting 1 point. The math is wrong until the 7th frame where is ends up showing the correct score. Lana's score is correct, except on frame 9 it shows she knocked over 6 pins on her first ball and is on her 2nd ball, but when it cuts to her, all 10 pins are up. Plus an unfinished 9th frame shouldn't show a score.
Audio problem: At the beginning, you hear the horses braying and the dog barking, but you can tell none of the animals are making those sounds. The sounds were added in afterwards.
Character mistake: Chloe is looking at her digital wall of weird for anyone with camouflage abilities in the past and says there's no match. They act like this is a new power. However, in season 1, "Shimmer", Jeff Palmer had the ability to turn invisible because of a cream he made with kryptonite infused green roses. That should have popped up in her search. And even if it didn't, Chloe should remember the ability to turn invisible because she got the cream on her fingers, which turned invisible.
Continuity mistake: When Lana goes to see Lance, who's packing up the serum, you see 5 syringes strapped in, 1 with serum in it. When Lance hits Lex and his case falls open, you can see the 5 syringes still strapped in, but now none have any serum in them. When Lance goes to pick up the case, only one syringe is strapped in, and it's in the wrong spot, next to some blood, and one syringe out of the strap lying in the open case.
Other mistake: Lois' car has the plate number "AJH 927." This is the same plate number that Senator Jennings had on his car in a previous episode, "Exposed."
Continuity mistake: In the shot of Lana being stepped on by the horse, her right arm is out by her side and her hair is covered with the wood shavings lining the stall. In the next shot of her, her right arm is up so that her right hand is by her head and her hair isn't covered with the shavings. Her arm is back out by her side in the next shot when Clark arrives.
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.
Continuity mistake: The "Go Crows" sign Lana is working on changes depending on the camera angle. From the front you can see the! at the end. In the close up shot of the sign, the! is now gone. When Lana underlines "crows" it's back but the writing is slightly different.
Revealing mistake: When Lionel is playing the piano while talking to Lex, you see inside the piano and none of the dampers are moving for the notes he's playing, revealing he's not really playing or even hitting the keys.
Continuity mistake: When Lex has the envelope and pulls it away from Lana as she grabs for it, the flap is opened, so the wax seal is on top. In the next shot the flap is folded down.
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