The exterior shot of the building where the party Madeline and Louise go to is the same exterior shot used for Monica's building on Friends (1994-2004).
In later releases of this episode, the 'kittens in a toilet poster' has been digitally replaced. This could possibly be due to a rights issue.
When Rory's classmates pull up to the Gilmore house, Lorelai remarks facetiously that Paris must have done a lot of babysitting to afford her car. The car that Paris drives is a BMW 330Ci.