Plot hole: Clark is crippled throughout much of the episode due to there being kryptonite in the tunnels. At one point he gets a rock stuck in his arm and he bleeds from this wound. For much of the time after this he has blood running down his arm from this wound. After he gets out of the tunnel he is healed but the problem is the blood from the wound also disappears. The actual wound should have healed up but the blood from that wound should still be shown staining his arm.
Factual error: Lana is trying to find out what Lex is up to. She gets a hold of his briefcase and takes it to the mansion where she shoots the locks off the case. When she does the case jumps a little bit but this is far less than it should. She is shooting at it from less than a foot away. The force of the bullet should have sent that case sliding across the desk at that range.