In this episode when Carol offers to help Marcia with
her homework Marcia says "This is math" insinuating that Carol is bad at math, but in "Alice Doesn't Live Here Anymore" Greg says Carol is a wiz at math.
Marcia reads the father of the year advertisement and decides she has to go out and mail the letter before midnight. The kids were in bed so it has to be at least 8:00, I have never heard of a post office that is open that late, let alone a mail box
pickup. If the letter had to be post marked by midnight it was too late to mail it anyways.