Revealing mistake: In the scene in which Jonathan shoots Lex, he is gently lowering and raising the barrel of the gun whilst shooting, even though there is a 'bullet-time' effect in progress. Maybe the sequence is shot in real-time, with the actors standing still and the 'bullet' added afterwards? Furthermore, would Lex really move that quickly in relation to the speed of the bullet?
Continuity mistake: After Lex confronts Desiree about changing her name, Lex says 'we really need to discuss this' Desiree then kisses Lex and they both tilt their heads to their left. Cut to a different angle and they are both tilting her heads to the right.
Continuity mistake: When Lana was making a video to send to Whitney, we see her interviewing Clark. We first see Clark through the camera's view finder. Lana then drops the camera (pointing it down) such that we see Clark's feet. Cut to a different angle but now Lana's is pointing the camera at Clark's chest level.
Continuity mistake: When Desiree walks into Clark's barn to work on their 'student-teacher relations', she holds her hair up with her right hand as she complains about the heat. She then lets her hair down and fixes it. Cut to a different angle and she is letting her hair down once again.
Continuity mistake: In Jail, when the sheriff tells Chloe and Lana that visiting time is over, we see Clark holding the bars with his left hand as he tells the girls that his dad went to see Desiree. Cut to a different angle (from inside the jail cell) but now Clark is no longer holding onto the bars and only holds them a few seconds later.
Continuity mistake: When Clark decides to stay home from school because he cannot control his heat vision, his father decides to have a talk with him. Jonathan pulls his son to face him and them places both his hands on Clark's shoulders. Cut to a different angle as Jonathan says: 'Clark, look at me ' but now we see his left hand on Clark's neck. Cut back to the previous angle and his hands are on Clark's shoulders again.
Revealing mistake: In the sheriff's office, the door to the jail area has no lock plate on the wall.
Continuity mistake: When Jonathan goes to talk to Desiree, we see her getting out of the swimming pool. However her hair is just damp when it should have been completely wet and dripping all over the place considering the length of her hair.
Continuity mistake: When Jonathan goes to talk to Desiree, Jonathan throws Desiree a bathrobe. She then proceeds to put it on and lifts her right hand over her head as she does so. Cut to a different angle and now she is raising her right hand over her head once again.
Continuity mistake: Pete arrives when Lana was interviewing Clark for a video that she would send to Whitney. Lana then asks Pete: 'want to give it a shot?' We then see Lana holding the view finder of the camera with her left thumb and index finger while the rest of her fingers in outstretched. Cut to a different angle (as we see Pete) but now the rest of her fingers are no longer outstretched.
Plot hole: When Clark uses his heat vision to heat the metal door handle to prevent Desiree from escaping, he only heats one handle. I know that things were happening fast, but it wouldn't have taken him that much more time to heat both handles, which he should have done since there is no way he could have known that she would have tried that particular handle.
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