Plot hole: Jack and Joey are desperate to get the tank pump fixed so they can put the lobsters back in. However, once the customer tells them how to fix it, they then stop for a chat, check his table for tips, read a poem, share a moment, and start cleaning counters - with no attempt to re-house the lobsters.
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: 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)
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.