When writing answers on his European geography test, Puck writes "Hartford, Hereford, Hampshire" in a row of three. When he gets the graded test back, "Hampshire" is written under "Hartford."
When Rachel is talking with Kurt about his audition, she's dressed in a white dress and her hair is permed. But when Kurt is singing his song and during her audition after Kurt, she's in a black dress and her hair is straight.
In voiceover, Rachel says "no dairy" as a rule for herself when preparing for a big performance, but it's already been established that she's a vegan, so "no dairy" is moot.