Character mistake: During the state game, Mouth starts to announce information about the game. You can see him in the background, however, his mouth is closed and he isn't speaking until it changes to the next clip. (00:28:00)
Songs to Love and Die By - S4-E10
Visible crew/equipment: When Keith is racing down the hall, Lucas follows and the ceiling of the high school set is visible. (00:19:05)
Everything in Its Right Place - S4-E11
Character mistake: Lucas is seen placing flowers on Keith's tombstone, which states he died on January 23, 2006. In the next shot Lucas places a single flower on the grave of Jimmy Edwards, who died the same day and in the same scene as Keith, yet his tombstone states that he died on March 1, 2006.
Everything in Its Right Place - S4-E11
Character mistake: Brooke and Rachel are in the clean teen meeting and they are asked if they want to join. After both saying yes, the clean teen president hands them their shirts but calls Rachel Brooke, and Brooke Rachel. You can see their hair colors and they didn't change spots when she went to get the shirts.
Continuity mistake: When Lucas is with Keith at the graveyard in 4-10 and Brooke is standing in front of "Peyton's" tombstone, it says she died on March 1, 2006. Keith notes that she died on the day of the shooting. However in this episode Lucas visits Keith's grave where his tombstone says he died in January 2016.
Revealing mistake: Haley's pregnancy pad is visible when she raises her arms while lying on the table. (00:21:15)
Prom Night at Hater High - S4-E15
Continuity mistake: In this episode a sex tape shows a fling between Brooke and Nathan, and it is supposed to be from the past, but Nathan's hair is much longer and so obviously older in the video that it looks like it could have been filmed the night before, not from when he and Peyton were together.
The Birth and Death of the Day - S4-E20
Plot hole: In season 4, Haley finds out she is pregnant. It is presumably around February, since it is right after Nathan and Haley's vow renewals and after the school shooting. If she, let's say, was already a few weeks along, she would not have given birth in June at graduation, but in October of the following year, since it takes 40 weeks or 9 months for a baby to go to full term, not 5 months.
All of a Sudden I Miss Everyone - S4-E21
Continuity mistake: When all of the girls dance to the Spice Girls song "If You Wanna Be My Lover", during this scene Haley's shoes repeatedly change from high heels to trainers whilst she is dancing.
