Idina Menzel (Shelby) and Jonathan Groff (Jesse) both starred in Frozen (2013). Idina as Elsa and Jonathan as Kristoff.
Jonathan Groff who plays Jesse St. James and Lea Michele who plays Rachel performed the lead roles in the Broadway musical of Spring Awakening.
First appearance of Jonathan Groff as Jessie St. James and Idina Menzel as Shelby Corcoran.
In one scene Kurt says that because of his voice people would think he was his mother on the phone. In interviews Chris Colfer said that that happened to him in real life when in one interview joked it was when his dad was calling.
In the library, just before Rachel picks up "Hello" by Lionel Ritchie, she looks over the sheet music for "Hello Again" from "The Jazz Singer", which is featured later in the episode.