When the teacher re-introduces Brad Langford (Adam Wylie) to the rest of the class, she mentions that he is returning after a run on Broadway in "Into the Woods". Wylie actually did perform with the Broadway cast of "Into the Woods".
In an earlier episode of the third season, Rory calls Lorelai "Pamela Des Barres" after Zack hits on her. The book Lorelai is reading in the opening scene is "I'm With the Band: Confessions of a Groupie" by Pamela Des Barres.
In the UK, Gilmore Girls premiered on Nickelodeon (UK) in 2003. Only the first three seasons were shown, with episodes edited for content and some, like "The Big One", were dropped entirely.
Liza Weil (Paris Geller) & Dakin Matthews (Hanin Charleston) also worked together on Gilmore Girls: A Year in the Life (2016) as the same characters, as well as on The West Wing (1999) as Karen Larson & Simon Blye respectively.