Revealing mistake: While there was a close up on Clark while he was asleep, you could see a small cut right above his eye, which is impossible if he can't be hurt.
Revealing mistake: When Lionel Luthor visits the Kent Farm and tells the Kents and Chloe that Lex is missing, Allison Mack is laughing when the group is shown from Lex's viewpoint in the barn.
Revealing mistake: When Clark split's the fence at Belle Reve, just before he pulls it apart you can see the breakaway part of the fence. It is a silver color compared to the gray of the actual fence and runs vertically in front of Clark and between where he puts his hands.
Revealing mistake: Lana and Clark are supposed to be skinny dipping at Crater Lake. When Clark pops up out of the water and goes "boo" to Lana she spins around and splashes Clark for making her worry. As she starts to splash Clark her body comes out of the water far enough to see she is wearing a tan tube top instead of actually skinny dipping.
Revealing mistake: When Nicholas throws the lighter it is supposed to be lit so that it will light the gas and kill Lana but as it flips through the air, before Clark grabs it, the lighter has no flame at all.
Revealing mistake: At the beginning of this episode Lana is supposedly naked. However, when she dives off of the pier, she is wearing a pair of red shorts.
Revealing mistake: Loder gets scared and tries to get away from Kara. He takes off down the road at a significant rate of speed. Kara uses her super speed to get in front of the car. Loder has to slam on his brakes to keep from hitting her. At the speed Loder was going at he should have either skidded to a stop or hit Kara with his car. Loder is able to stop his car without doing either.
Revealing mistake: The computer that Molly takes the hard drive from is shown as having no power cord plugged into the back of the unit. With no power being supplied to the unit the hard drive would not be displaying a picture on the monitor, the monitor itself maybe plugged up but no signal from the computer would be going to it, and we see that the wallpaper on the screen is immediately taken off when Molly unplugs the hard drive.
Phoenix (2) - S3-E2
Revealing mistake: When Clark rips the door off the Lincoln, you can see there's no interior panel or door glass.
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