Revealing mistake: As Tyler slides across the floor, after Clark knocks him out of Whitney's father's room, he hits the camera. When he does the camera has a noticeable shake to it because of it.
Smallville (2001)
1 revealing mistake in Reaper - chronological order
Other mistake: Lois digs up Chloe's grave site to unearth her casket. It is obvious that the casket is not buried six feet deep. You would think, with all that is going on, that LuthorCorp would have at least buried the casket deeper to deter inquisitive eyes and maybe throw in a few scattered bones for good measure.
Jonathan Kent: Are you okay?
Clark Kent: Can I answer that in about five years?
Jonathan Kent: Yeah.
Clark Kent: Dad I'm glad you and mom are the ones that found me.
Jonathan Kent: We didn't find you, Clark, you found us.
More trivia for Smallville
Question: Throughout the series, people mutate fairly soon after their exposure to kryptonite. Is it ever explained how Lana has managed to wear a piece of kryptonite around her neck for 12 years and not change?
Answer: The kryptonite only creates mutations when it reacts with the environment and an individual. Remember, the FDA and several environmental groups did check out Smallville after the meteor shower, but found no danger in the rocks. Obviously they're not always emitting mutating rays, or all the flora and fauna of the surrounding area would be horribly mutated.
Phoenix