The house exterior standing in for The Dragonfly is actually the exterior used for the house on The Waltons (1972). It was dismantled from its original lot location that was used when filming the Waltons, and was placed on another set for Gilmore Girls.
Emily and Michel talk (in French) about Paris and how Emily went there each year in Spring. A few episodes previous, Emily and Richard seemed outraged by the idea of going to Paris (and Europe in general) in Spring, insisting they only go in the Fall.
This episode is the first time we see Luke's apartment.
Rachel asked Lorelai if she wore contacts and Lorelai said no but in the first episode, Loerlai said she thought she put her contact in backwards.
Emily seems shocked when she sees where Lorelei and Rory used to live but in a previous episode Lorelei told Sookie that Emily would come visit Rory as a baby when she lived at the inn meaning she would've already seen it.