Revealing mistake: Lana and Clark are supposed to be skinny dipping at Crater Lake. When Clark pops up out of the water and goes "boo" to Lana she spins around and splashes Clark for making her worry. As she starts to splash Clark her body comes out of the water far enough to see she is wearing a tan tube top instead of actually skinny dipping.
Revealing mistake: Loder gets scared and tries to get away from Kara. He takes off down the road at a significant rate of speed. Kara uses her super speed to get in front of the car. Loder has to slam on his brakes to keep from hitting her. At the speed Loder was going at he should have either skidded to a stop or hit Kara with his car. Loder is able to stop his car without doing either.
Revealing mistake: The computer that Molly takes the hard drive from is shown as having no power cord plugged into the back of the unit. With no power being supplied to the unit the hard drive would not be displaying a picture on the monitor, the monitor itself maybe plugged up but no signal from the computer would be going to it, and we see that the wallpaper on the screen is immediately taken off when Molly unplugs the hard drive.