You're Never Fully Dressed Without a Smile is from the musical Annie. Sarah Jessica Parker played Annie on Broadway in 1979.
During the final scene, Rachel is listening to "Moon River." Melissa Benoist performs this song as Supergirl during The Flash crossover episode, 3.17 Duet, which featured Darren Criss.
This isn't the first time a Sarah Jessica Parker (Isabella Wright) character worked at Vogue. In Sex and the City (1998), Carrie Bradshaw was a freelance write for Vogue.
First appearance of Sarah Jessica Parker as Isabella Wright, Kurt's boss.
Isabelle Wright tells Kurt that she is from Columbus when she points out he is from Lima upon meeting him at his interview. Sarah Jessica Parker is in fact from Ohio, but unlike her character, Parker is from Nelsonville (about an hour southeast of Columbus).