Continuity mistake: When Clark, Pete and Chloe were searching for Clark's father in the woods, they stumble upon a motor home dropped by the tornado. Chloe then picks up a Nixon's camera and looks at it. Cut to Nixon and Jonathan Kent then back to a wide shot as we see Chloe throwing the camera down onto the ground. Clark then uses his X-ray vision once again. Cut back to a wider angle (as they walk away) yet we see Chloe throw down the camera once again.
Factual error: Chloe wants to access the security camera files on the Luthor mansion server to see what happened to Lex. She can't crack the password, so she says she'll just download the entire hard drive. She pulls out a thumb drive and proceeds to do so. Two big technical problems here. Firstly, if she can't log in, she can't access anything on the server. And Secondly, the entire hard drive for a server (which is huge) containing video files (which are huge) will not fit on any thumb drive.
Continuity mistake: While Chloe and Clark are on the horses, and Chloe is talking about the surveyors from Rickman Industries, when the shot is on Chloe's side, Clark is holding his reins in his right hand which is resting on top of his left. When the shot switches to Clark's side, as Chloe continues the story, and now Clark's right hand is under his left.
Audio problem: When Clark and Manhunter are in his Barn talking about how to stop Bizarro and figuring out the yellow sun can heal Clark, there is a beep of a watch or someting similar in the background, but neither Clark nor the Manhunter react to it, which means it happened off screen and unintentionally.
Continuity mistake: When the offensive line is first shown, as they sit on the bench, the shot is of them from behind. In that shot the team jersey numbers are in this order 89, 46, 8, 66, 1. Then the camera view changes to be in front of the players only now going from the players left to their right is 99, 46, 8, 66, 89.
Continuity mistake: During the flashback that happens at the Luthor mansion, the one that starts with the cup shattering on the floor, young Lex is shown peeking through a slightly cracked open door. Just after Lionel asks the nanny to give him Julian there is a shot of Lex peeking in and you can see that he has hair on his forehead. Now Lex, at this point, would have been bald, as a result of the meteor shower in Smallville for several years and would have no hair at all on his head in this flashback. In fact when Lionel finally realizes that Lex is outside the door we see that Lex has no hair on his head.
Plot hole: During Clark's rescuing Lana from the fire in the basement, Clark wakes Lana just before he is grabbed by the coach. Clark then tosses the coach all the way across the room and into a wall. Lana makes no mention of how Clark could toss a full grown man across a room like that even though it happens right in front of her face.
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.
Continuity mistake: As the two racers speed past Clark and Martha, in the truck at the intersection, Pete's red car does not have its neon lights on in the back window and under the rear spoiler. Then in the next shot, while still racing, both the blue neon lights in the back window and the green neon under the rear spoiler are on.
Continuity mistake: After Clark saves Lex from the ring of fire we see the area that was burned by the fire. The candle that Shannon used to light the alcohol is no longer on the floor. Since the candle was in the fire it should be partially melted and there would be some evidence of it.