The first time we are made aware of Gunther's love for Rachel.
The Mattress King is referenced in the Frasier episode Hot Pursuit (2000), when Niles (David Hyde Pierce) talks about expecting cheating from a mattress king but not a garbage king.
Rachel's dad tipped 4% on a $200 bill. That means he only tipped $8.
Rachel says that if she squints then Ross could look like Alan Alda. Jennifer Aniston is in The Object of My Affection (1998) where Alan Alda plays her brother-in-law.
When Chandler is 'driving' the bed, the mattress is lower than it was earlier. Previously, it was almost even with the sides of the bed but when he is sitting on it clearly one of the mattresses have been removed.