Other mistake: Throughout the episode, including the very first shot, we see the sun is shining brighter and hotter than usual. This lends credibility to the theory that Superman's powers are responsible for increased solar activity. Later on in the episode it is revealed that the heatwave is being orchestrated by Lex Luthor, who is is heating an underground river to coincide with Superman using his powers. Lex does not however have any control of the weather, and no explanation is offered for why the weather conveniently 'played along' with his plan.
Character mistake: When Clark flies to see his parents for the first time, he is wearing a maroon shirt and jacket. When he lands at his parents farm he is still wearing his jacket and maroon shirt. In the next shot, he has taken his jacket off which now has a rip in the shoulder, as he enters the house his shirt is blue, and then in the following shot at the table having dinner his shirt is again maroon. (00:30:00 - 00:30:50)