As Clark and Lana enter the room with the tubes containing the Emily clones, a long shot shows three large glass beakers in the foreground, which are all empty. The beakers are on a stand near the farthest tube from Clark and Lana. A few shots later, Lana peers into this tube and is startled when the clone opens her eyes, causing Lana to jump back into the stand, thus knocking over the beakers, which all now contain green liquid Kryptonite.
When Clark and Lana are investigating in Emily's room Clark picks up a reel of movie film and unwinds some. It is clearly 16mm yet the projector that is on the same table is too small to be anything but an 8mm projector and the reels on it (both empty) are also 8mm.
When Lana asks Jonathan to borrow Clark for a few minutes you hear two other people reply 'yeah, right' when Jonathan opens his mouth and then Jonathan finishes the rest of the sentence.