Continuity mistake: As Chloe and Clark talk about their feelings the shoulder protector/pad of Clark's backpack switches position with no help from Clark. At first it is more in front and showing more than a few shots later, again with no help from Clark by shifting the backpack, it is more on top of the shoulder and not as visible.
Continuity mistake: The position of Clark's sleeve to the tourniquet change between shots. When Dr. Bryce first ties the tourniquet she does so at about an inch from the end of the sleeve. In the next shot, as Clark lies unconscious and nobody touches his sleeve, the tourniquet is tied around the sleeve and no longer on his skin. Just before Dr. Bryce sticks the needle in it's back to being an inch from his sleeve.
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.
Factual error: Alicia gives Clark the necklace with red kryptonite and this causes him to break Alicia's bracelet a few shots later. She then is able to teleport once it is removed. Now, according to the story, that bracelet prevents her from teleporting by releasing 'trace' amounts of lead into her bloodstream. If that were the case she would have to wait until the trace amounts were cleared from her system to start teleporting again.
Continuity mistake: Clark tells his parents that he went to see his grandfather and that he asks to give the cashiers check to his mom. He takes it out of his pocket with his right hand and Martha Kent takes it with her left hand. Cut to a different angle but now it is Martha's left arm which is see being pulled back to her body as if she took the check using her right hand instead.
Audio problem: After Clark's parents come home, after their anniversary dinner, Jonathan and Clark go to see Earl in the hospital. As the Doctor says "It looks like he's got some sort of mineral poisoning, but its not from any mineral I've seen before." For the first few words of that line her mouth does not match up to what is being said but the dialogue, and her mouth slowly come together at the end of the line.
Visible crew/equipment: When Prof. Joseph Willowbrook and Lionel Luther walk down the steps of a building, talking about the possible whereabouts of Jeremiah Holdsclaw, they begin to cross the courtyard, which is bathed in sunlight. As they walk across, and eventually walk under another building, as they cross the courtyard, you can see the shadow of a large reflector board moving along with them as they walk.
Plot hole: Clark is delivering presents for Chloe. In the overhead shots looking down on Metropolis he super speeds from building to building and he only spends like one second in each building before going to the next one. This doesn't match what is shown while we see him leave presents by the various trees inside the apartments. In those interior shots he spends 5-10 seconds in each room. The overhead shots are not sped up. Not only do these times not match up but he would also be slowed down to open the doors or he would constantly be breaking them down.
Continuity mistake: When Clark's parent show up at the house Clark hurries up and acts busy. He grabs 4 boards and moves them from one part of the kitchen to the other and leans them up against the wall. When Clark turns around to face his parents there are only 2 boards leaning on the wall.