This episode was "Dedicated To The People Of New York City" following the attacks on September 11, 2001.
The girl who Joey is instructing on tennis moves is the same girl who sees Rachel take the key to Monica's Porsche (along with money) from Ross' jacket in The One with Chandler's Dad (2001).
Phoebe lies and tells everyone that she's pregnant with James Brolin's child only to be told that he is married to Barbra Streisand. 'Elliot Gould' (who plays Monica and Ross' father, Jack) was married to Barbra Streisand before she subsequently married Brolin.
When Monica and Chandler get engaged, Monica finds Rachel and Ross kissing in the hallway and accuses Rachel of stealing her thunder. To get her back, Monica states that when Rachel gets engaged, Monica is going to announce that she is pregnant - thereby stealing Rachel's thunder. However, it is Rachel that announces on Monica's wedding night that she is pregnant.
On the epsiode that aired, when Ross is seated at the kids table, his son Ben is seated next to him but neither acknowledges the other. On the DVD uncut version, Ben asks Ross, "Dad, can't you go back to your table?"