Other mistake: In the opening credits Kristin Kreuk's first name is misspelled as "Kristen." The credits sequence, which was new for Season 5, was corrected by the time the second episode of the season aired.
Other mistake: When he takes Lana to the Fortress of Solitude, Clark squeezes a rock and when he opens his hand we see a perfectly cut diamond. Problem here is that in the real world, diamonds don't come out of the earth already cut and shaped. (00:04:20)