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.
Character mistake: Chloe hands Clark a newspaper with the list of jury members from Harry Volk's trial. As he reads the list he says "Rudolph Gage, Rita Garfield". After Clark realizes that his grandfather, Hiram Kent, is on the jury he hands the paper to Lana. A shot of the newspaper has the jury members listed as Randolph Gage, and Eve Garfield. Even young Harry calls her Eve when confronting Zoe at The Beanery.
Continuity mistake: Jason Teague arrives at the Kent farm. He fires a shot into the windshield of the Kent's truck. So we obviously know the gun is loaded. Later, inside the Kent's house, Jason still has Jonathan and Martha held hostage. After Jason mentions the symbols burned into the field Martha says she doesn't know what he is talking about. Jason gets upset and racks the shotgun but when he does no shotgun shell, used or unused, is ejected. Now Jason would have had to keep the gun loaded while moving Jonathan and Martha back to the house as he would have had no time to unload and reload his gun.
Continuity mistake: As the car that Jason was in comes to a stop after the crash you can see Pete's red car is nowhere near the wreckage of Jason's car. In the next shot Pete's car is shown rolling forward to a stop, meaning he hadn't backed up but was still going forward and stopped where he was, but now Pete is only 30-40 feet from the wreck of Jason's car.
Continuity mistake: After Lex tells Martha that he'll do whatever he can to help Jonathan, she goes into Jonathan's hospital room. As she goes through the door, the blinds next to the door are closed. When the shot switches to show Clark standing at the other window, the blinds next to the door are open. Then, as Lex goes over to Clark, the blinds next to the door are closed again.
Revealing mistake: The computer that Molly takes the hard drive from is shown as having no power cord plugged into the back of the unit. With no power being supplied to the unit the hard drive would not be displaying a picture on the monitor, the monitor itself maybe plugged up but no signal from the computer would be going to it, and we see that the wallpaper on the screen is immediately taken off when Molly unplugs the hard drive.
Continuity mistake: When Jonathan is sitting down, before he tells Clark that he can't always be honest, in the shot from the other side of the table Jonathan is holding a book in his right hand as he is sitting down. When the shot switches to Clark's right, Jonathan is still starting to sit but now the book is in his left hand.
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.