Jack Geller tells Chandler that Judy's parents never found out he wasn't a lawyer and tell Chandler, "if you ever see me giving them legal advice, just nod along." However, Judy's mother died in season 1.
In a previous episode, Rachel stated that she does not know how to sail. However, in this episode, she is a trained sailor and teaches Joey how to sail.
Phoebe states that she swore to her grandmother "... on her deathbed..." that she would safeguard the cookie recipe. However in The One with Joey's Bag (1999) her grandmother died at a hospital after having collapsed and becoming unconscious at the market. According to Phoebe, her last words were ".. Okay dear you go get the eggs and I'm gonna get the yogurt and we'll meet at the checkout counter".
In the beginning when Phoebe asked what they wanted as an engagement present, Chandler announces they won't be having an engagement party. However, a few episodes later, when talking to Chandler's boss, Monica announces that they had not invited him due to the way he had acted at their engagement party.
When they go into the whirlpool room, Jack and Chandler hang up their dressing gowns but when Chandler realises he should have worn shorts he takes Jack's robe back off of the peg instead of his own to cover his modesty.
When they are in Monica and Chandler's apartment telling the story about how Chandler sat on Jack's lap, the phone rings. Chandler says, "If that is your father calling to tell this story then the marriage is off!" However, you can clearly see that Matthew Perry/Chandler actually says, "If that is your father calling to tell this story then the wedding is off" but the audio was dubbed over the say "marriage" instead of "wedding".
When Ross complains about not getting engagement presents in the past and states he's been engaged twice, he could've been talking about Carol and Emily. However, later he's talking about it with Rachel who says they didn't get any presents, to which Ross answers "thank you". Rachel and Ross never were engaged, they married in Vegas due to drunken whim.
When Joey and Rachel are sailing Joey complains about the Coast Guard ship being in the wrong place, saying that he coast is "over there," while pointing off to his right. With the World Trade Center behind him, he would be pointing up the Hudson River. He should have pointed off to his left.