Revealing mistake: After Lana is warned by Chloe that Clark has gone all 'Captain Paranoid', she examines the silver 'meteor rock' more closely. We see a shot of her hand holding the 'meteor rock' but the hand that is shown is obviously not Kristin Kreuk's hand.
Continuity mistake: Clark is poisoned by a silver kryptonite splinter. When Clark is stabbed, the splinter is in his left index finger. Then, in the scene with Fine after class, (less than twenty minutes later,) Clark is seen rubbing his right index finger.