Continuity mistake: The meteors are shown traveling together in space at the beginning, but the smoke trail from the first meteorite runs perpendicular to the flight of the next one. They should be falling along roughly the same flight corridor, as all the other meteorites do. (00:00:10 - 00:04:30)
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 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)
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)
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)
Continuity mistake: When Jonathan lectures Clark about the danger of accepting gifts from Luthors, the key he twirls is a GM truck key, not a Ford truck key.
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: While researching Greg with Chloe, Clark changes from one hand on the computer mouse to arms crossed and back. (00:34:00)
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: Clark's hair goes from long to short and back to long as Clark, Pete and Chloe talk about Greg's tree fort.
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.
Continuity mistake: While Clark and Jonathan are talking about Clark being on the football team, Jonathan puts his hands on Clark's shoulders. Between shots, the position of Jonathan's hands on Clark's shoulders repeatedly changes.
Continuity mistake: When "Lex" threatens the bank manager, he points the gun at his face, but the next shot on the manager shows the gun at his throat. (00:01:35)
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