Lois hands two boxes of decorations to Clark for Chloe's party but in the next shot he is holding just one box. The box reappears when they turn to go into the barn.
You can see the string used to pull Clark's shotgun away in the cave seconds before it's yanked away.
From 40:25 until 41:25 the reflection of the camera lights and equipment can be seen reflected in Lana's right eye when the camera is focused on her.
It is interesting as to how Clark shaves or has his hair cut, seeing that the scissors broke when Lana tried to cut off a lock of his hair.
In "Crusade", Chloe's gravestone clearly lists her birth year as 1987 meaning it would be her 17th birthday in 2004. This episode proves the birth year on the gravestone to be a production error because Lois tells Clark the party is for Chloe's 18th birthday, and Chloe states the same in the deleted scenes. Also, it is unlikely Chloe would start her high school senior year at age 16.
In previous season (s03e12 - Hereafter) when talking to Adam, Lex says that he does not play the piano (that he had never had patience to practice), and now he is playing it well.
When Lana shows Jason, Isabell's spell book she say it is Countess Isabell Marguerite Theroux's, flipping her name which really is Countess Marguerite Isobel Theroux.