Deliberate mistake: After the party, in the scene where Lucas goes into the cafe, he finds Haley crying. The shot is a distant shot with Lucas and Haley in it. Haley's hands are covering her face. In the next shot, just of Haley, her one hand is over her forehead.
In one of the first episodes of the second season, Brooke is talking to Peyton about Lucas, and she says "love triangles are so last season". In the first season, Brooke, Peyton, and Lucas were in a love triangle.