Other mistake: Lois digs up Chloe's grave site to unearth her casket. It is obvious that the casket is not buried six feet deep. You would think, will all that is going on, that LuthorCorp would have at least buried the casket deeper to deter inquisitive eyes and maybe throw in a few scattered bones for good measure.
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.
Audio problem: Clark listens to his father and Earl talking in the hospital through the visitor window. The sound is the same volume and quality as when Earl was using the microphone, which he is not using now. Even if Clark used super-hearing to eavesdrop, it wouldn't sound the same as the microphone.
Revealing mistake: When Tina puts the necklace on Clark to disable him, he falls to the ground of his barn. As he is lying there, his collar is very dark, and his shoulder is lit up. Since the source of the green light is supposed to be the necklace, his collar should be the brightest lit.
Continuity mistake: When Lana shows Chloe the picture of her mother and Henry Small. We see that Chloe holds the picture on its bottom corners with both her hands. Cut to a close up of the picture but now she is holding it in the bottom middle of the picture. Cut back to the previous angle and she is holding it by the corners once again.
Continuity mistake: When Chloe is first asking Pete and Clark the questions for her poll you can see that the top page on her clipboard is yellow. Then she shows it to Lana and the camera gives you a nice big shot of the front piece of paper and it is white. When Chloe says "its unleashing the inner Lana." the front of the clipboard is shown again and now the paper is yellow.
Plot hole: Chloe says the coroner found teeth marks on the foreman's bones. During the attack, at the beginning of the episode, the foreman only got a couple of scratches on his face and the rest of his clothes were perfectly fine and hadn't, in any way, been torn up. It would have taken the wolf tearing through the clothes, through the skin and, finally, through the muscle to leave any teeth marks on the foreman's bones and that did not happen.
Revealing mistake: In the scene in which Johnathan shoots Lex, you can see 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: As Clark first gets to the bridge at Cherry Hill, the shadows establish the time as either early morning or early evening since the shadows are long. In several shots during this scene the sun suddenly jumps to around noon as the bridge shadow goes from sticking out far to one side to being almost directly under the bridge and the shadow of the semi shortens when Clark is making his super jump.
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: In the head on shot of the car that almost hits Mr. Altman you see the driver of that car react by turning his car to the left. In the very next shot, as Clark and Mr. Altman are just coming to a stop after Clark's high speed rescue, the driver is now turning his car to the right, as shown by which way his wheels are turned.
Continuity mistake: As Lionel's cellmate tells Lionel "I've always kind of had a thing for pattern recognition." the shot changes mid-sentence. Between changes Lionel's cellmate goes from having his arms crossed, hands holding his elbows, to having his hands almost clasped together.