The Games That Play Us - S1-E22
Other mistake: In the last episode of season 1, Lucas goes to see Haley and Nathan where they tell him they got married last night, which must have been after the playoffs game. However, in season 2 in flashbacks of their wedding they got married during the day.
The Worst Day Since Yesterday - S3-E8
Other mistake: At the start of season 3 it is established by Whitey that the lockers are in alphbetical order, hence why Nathan, Haley and Lucas all have lockers next to each other, but in this episode when Haley and Rachel decorated the Scott brother's lockers, Brooke then goes to her locker and is sad when she opens it as Lucas decorated it earlier in the season. Brooke's locker however is only a few lockers away from Lucas', even though they are meant to be in alphabetical order.