Continuity mistake: After the meteor shower, the bit of hair that Mr. Luthor finds in the cornfield changes in his hands from stretched straight to curled. (00:06:15)
Visible crew/equipment: When Clark finds Lex in the Luthor mansion, they walk down the hall and into a new room. As they enter, as Lex is saying "So, hows the new ride?" if you look in the bottom left of the screen you can see a white tape marker on the floor, where Lex will walk over to subsequently. (00:33:10)
Continuity mistake: The hole in the guard rail changes size and shape between the shot of Lex driving off it and another looking up at it from below. (00:18:10)
Visible crew/equipment: When Lex spins up to Luthor Corp in his car, as the camera pans over the car to follow him, the cameraman is reflected in the window as he pans over. (00:14:40)
Continuity mistake: In the truck right before the parade passes them by, Jonathan Kent kisses his wife. Cut to a different angle but this time his left hand is on her cheek. It wasn't there in the prior angle. (00:02:15)
Continuity mistake: After Greg hits Clark with the pipe in the foundry, Clark's hands are very dirty. In the closeup on Clark's hand immediately after he lands, the hand is clean to show the effects of the Kryptonite. (00:39:45)
Continuity mistake: Despite the fact that Clark and Jonathan are looking in the rafters above them for Greg, their flashlights stay relatively level. (00:26:35)
Continuity mistake: When Lex is about to hit Clark with his car, Clark alternates between facing the car and facing the bridge. (00:17:20)
Revealing mistake: Once Victoria has drawn her bath, we see her get in, and then lean back into the water. However she is already wet on her chest and her hair is damp already. This is probably due to previous takes of the same scene.
Continuity mistake: As Lex is chalking his pool stick while talking to Dominic about cutting 20% of the workforce at the LutherCorp Smallville plant, there is a red snooker ball on the wall rack missing from the second row. When Lex walks over to the other end of the pool table, the camera shot changes back to Dominic, now there is a ball missing from the top row, which was not missing before.
Plot hole: Chloe writes her phone number on Sean's hand. It disappears when we see him struggling against the ice of the lake, then reappears in the scene where he is calling old girlfriends. And how exactly would pen ink survive several hours submerged in water and then another eight hours of normal activity without becoming blurred? (00:04:15 - 00:19:50)
Continuity mistake: Tina's grip on Lana's necklace changes as she stands over Lana's body. (00:37:30)
Continuity mistake: While researching Greg with Chloe, Clark changes from one hand on the computer mouse to arms crossed and back. (00:34:00)
Continuity mistake: When Amy is introduced, she is writing about two lines down from the top of the page in her journal. After Troy snatches it, the writing runs about halfway down the page. (00:00:35)
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