When Mr. Carlton's son reaches into the sink to pull out the plug, the plug is sitting on the counter next to him. He then proceeds to pull it out of the sink and set it on the counter.
When we first see Dean, he is circling the girl's picture in the newspaper. When he shows the paper to Sam, the circle is different. He originally circled her name as well, but it wasn't circled on the paper Sam had.
When Will Carlton is chopping potatoes for dinner, the sink plug is on the counter. When the sink begins to fill, the plug is in the drain.
When the boys are trying to stop Mr. Carlton from taking his boat out into the lake, Sam quickly outruns Dean. However, by the time they reach the dock, Dean is back in front.
As Sam and Dean are driving to the church Sam's face is reflected in the window behind him. It should be the back of his head.
During the bathtub scene, the tub is filled to the brim, yet Andrea continues to let water flow into the tub. It never overflows. Contrarily, at one point, the tub has less water than before.
22 minutes in, when Sam and Dean are in the Impala (on their way to find the yellow house), you can faintly see Sam's reflection in the passenger window, facing the wrong way.
At 40:55 minutes, there is a mic cable visible below Sam's jumper as he is talking with Andrea.
There is no "Lake Manitoc" in Wisconsin.
At 5:11 a boom mic pops in at the top center while Will gives his line.
In the scene where Sam and Dean are at the end of the dock, trying to stop the boat, Dean is clearly replaced by a stunt man in one shot.