Continuity mistake: When Abbie and Jen are talking to Vincent on the dock, Abbie's sheer gold shirt is up to her shoulders in the long shots, but not visible in the close ups.
Crossroads - S2-E2
Continuity mistake: When Joey finds Dawson at Pacey's Pier Party, it is raining heavily. Both Dawson and Joey get soaked and their hair is very wet as they reunite and kiss. At this point, it suddenly stops raining and does not rain again the rest of the time at the pier. But later, when Jen and Abby are talking behind them, both times Dawson and Joey are shown from the rear their hair is noticeably dry, wavy and styled. Later, when Dawson and Joey are talking again before she goes home, their hair is once again very wet and combed flat against their heads. Also, neither Jen or Abby's hair appeared wet at all during the party.
Continuity mistake: When Pacey is at Andie's house waiting for their date, he picks up a family photo of the entire McPhee family. There is a close-up of this photo, and you can see all family members including Andie's dead brother, Tim, and her father. In addition to the Father in the photo not being actor David Dukes, there is a completely different person in the photo representing Tim, the dead brother, than the actor who portrayed him in Andie's delusions later in the season. The person in the photo is sandy blond haired, and the actor who later portrayed him in the show was a different person with very dark hair.
Continuity mistake: The first time Abby reads the "mystery letter" out loud, she says "But sex changes everything." The second time, she reads, "But having sex changes everything."
Continuity mistake: When Andie and Jen are talking in the school bathroom, the mascara running down Jen's face disappears between shots.
Continuity mistake: When Pacey is at Andie's house waiting for their date, he picks up a family photo of the entire McPhee family. There is a close-up of this photo, and you can see all family members including Andie's dead brother, Tim, and her father. Look closely at the man representing her father in the photo. It is not David Dukes, the actor who later plays her father. Apparently this scene was shot/photo made before David Dukes was available. (00:26:05)
Continuity mistake: When Joey and Dawson are in the rowboat after their dinner date, they are kissing and talking. Just before Joey says, "OK, that's enough, Jumbo," there is a shot of them from the rear and Joey has her left hand up around the back of Dawson's neck, scrunching his hair. The very next shot shows them from the front again, and suddenly both of Joey's hands are down nowhere near Dawson's neck. The transition was too fast for her to have moved her hand.
Answer: It's only explained once in the series. Jack says to Andie "I tried to start kindergarten without you", meaning Andie was smart enough to start school early.