Continuity mistake: When Lois is strapped down on the cosmetic table, as she is struggling to free herself, the position of the strap that is holding her down over her chest, keeps changing how far on/off it is, on her breasts, between different shots.
Continuity mistake: When Clark first finds the necklace in the shower drain it is all in a single line with no loops or overlaps except at the very end. As Clark picks the necklace up it now has several loops and overlaps all along the chain and not just at the end where the clasp is.
Continuity mistake: When Clark looks over to Lana, while in the coach's office, she starts to pull up her right sleeve that had slipped down. As Clark says "Lana.what are you doing here?" the shot is behind Lana and her sleeve is down and is showing a lot of her upper arm and shoulder but when the shot switches back to the front of Lana, she has her sleeve pulled up covering most of her upper arm.
Continuity mistake: When the mirror falls on Lana and shatters on her, you can see that there are bleeding cuts on the left side of her face. However, for the rest of the episode, there are no cuts on the left side of the face (where they should be) but there are cuts on the right side of her face.
Suggested correction: When the mirror falls, we only see her left side. But in the hospital you can plainly see both cheeks were cut up, the right one a bit more. Throughout the episode though, the cuts on the left side never disappear and there just seems to be more shots of her right side when she's out of the hospital.