Visible crew/equipment: After the scene transition from when Clark throws Jonathan into the truck after being exposed to Red Kryptonite, the camera pans around Jonathan with his shirt off; on the left-side of the screen we see a man with sunglasses on who has no earthly right to be there just randomly on the Kent Farm. (00:16:23)
Plot hole: In this episode, Pete comes across Clark's spaceship in a field, where it landed after the tornadoes hit the town during the last episode of Season 1. The Kents knew the spaceship was gone, and of course it was important that they attempt to get it back as soon as possible so it doesn't fall into the wrong hands. With Clark's speed and X-Ray vision, he should have been able to find the ship after not too long of a search (especially since it was within a few hundreds yards of a road). It seems implausible that he would not have looked for it, given its importance.
Other mistake: The physics of what happens to the mallet after it hits the ring are completely unrealistic. No matter what the actual composition of red kryptonite contains, there is no way that it could reflect all of the force that was impacted upon it. Clark was also weakened by the green kryptonite. Jonathan's swing of the mallet and Clark's weakened strength would not have allowed him to keep his arm out after being struck by the mallet.
Continuity mistake: The woman uses her right hand to get a swab for DNA testing from Clark. At first, we only see her right hand near Clark's face. Cut to a different angle as she says "There, now that didn't hurt a bit did it?" but now her left hand is close to Clark's face.
Continuity mistake: When Clark arrives late for school in Lex's car, he is stopped by principal Reynolds who tells him that he should have been there four minutes ago and points at his watch with his right hand. Cut to a different angle but now he is pointing at Clark with his right hand.
Other mistake: Krissy's mutant aging reduces her to dust and ash within seconds. Oddly enough, it takes her non-mutant clothing with her. (00:36:45)
Suggested correction: First off, we don't know what gave her powers, there's nothing to indicate a mutation. Second, we see beams of light or heat shooting out of her, indicating she's more than just rapidly ageing like her victims. Her body seems to be burning, turning her and her clothes to ash.
Continuity mistake: While Clark is talking to the agent that he has pinned to the wall, with the billiard table, the balls near the gun change their positions between shots.
Continuity mistake: When the agent goes to the Luthor mansion and confronts Clark about Jessie's whereabouts, Clark uses his speed to push the billiard table into the agent and jams him against a wall. As he does, the billiard balls obviously move due to the force Clark put on the table. Cut to the agent and later on Clark and we still see the billiard balls on the table yet they are no longer moving. It was too quickly for an object in motion such as a billiard ball to come to a complete stop given the force Clark exerted on the table.
Continuity mistake: When Martha is in the kitchen and starts having a coughing fit from the toxin, she drops the pitcher of lemonade. The pitcher lands on its side and breaks, but in the next shot, the broken base is positioned upright, sitting level on the floor, the jagged broken edges waiting to impale Martha.
Continuity mistake: When there is a flashback of the shooting, the police officer is heard to fire 3 shots, yet in each other flashbacks it's 2 shots and there are only 2 wounds in the victim.
Skinwalker - S2-E10
Audio problem: In the barn, as Kyla and Clark talk about Skinwalkers, Clark says "like the legend of Naman is just a story?". When the shot switches to Kyla you can see Clark is talking but no dialogue is heard from him.
Continuity mistake: When Ian confronts Mr. Frankle about his grade, the teacher removes both his gloves and is about to raise his face protector. Cut to a different angle but now he has his right glove back on.
Continuity mistake: At the bar, the agent shows the barkeeper a picture of Jessie. Throughout the whole conversation, it is the agent who is holding the picture. However, when the agent says something about the legal drinking age in Kansas, it is the bartender who is instantaneously holding the picture.
Skinwalker - S2-E10
Visible crew/equipment: While Clark and Pete are riding dirt bikes, you can see a crew-member in a green jacket in the bottom-right-hand corner of the screen in the shot where they go off the jump. In the next shot he has disappeared.
Continuity mistake: After Clark finds out that Ryan is dying, we see him holding a comic book in the farm. His dad then arrives and he turns to look at him. He places his left hand to his side as he holds the comic book in his right hand. Cut to a different angle and now both his hands are together in front of him.
Continuity mistake: When Lex finds Clark in the Talon doing his essay, he sits and talks with him. He puts his cup on the table and puts his hands in front of him. In the next shot, Lex now has his arms crossed in front of him on top of the table.
Continuity mistake: Clark rushes to get to school in Lex's car and we see principal Reynolds closing the gate to the school. In the close up, we see that the principal is off to the left of the lock of the gate. Cut to a different angle (his back to the camera) just as Clark arrives in Lex's car but now he is standing in front of the gate lock.
Continuity mistake: The "Go Crows" sign Lana is working on changes depending on the camera angle. From the front you can see the! at the end. In the close up shot of the sign, the! is now gone. When Lana underlines "crows" it's back but the writing is slightly different.
Revealing mistake: When Lionel is playing the piano while talking to Lex, you see inside the piano and none of the dampers are moving for the notes he's playing, revealing he's not really playing or even hitting the keys.