When Joey comes in Rachel's hospital room in the very beginning, there is a wall behind him. In the previous episode, The One Where No One Proposes (2002), Rachel's door faced a long hallway.
It is revealed that Ross's birthday is October 18. However in the episode "The One with Joey's New Girlfriend (1997)" Gunther asks Rachel when her birthday is, claiming he is making a list of birthdays, when Ross begins to say his birthday, he says it's in December.
Monica, Rachel, and Phoebe are looking at Emma in the bassinet and she has on a pink hat and has a hospital blanket around her. A few seconds later when Rachel picks her up, Emma is wearing a different hat and has a different blanket.
At the restaurant scene, Joey's date Mary-Allen eats her cocktail olives, but in the next shot they are still in her glass.
In the hospital when completing the form, Ross says his birthday is on October 18th. But in The One with the Jellyfish (1997), when Joey and Chandler give him game tickets as a birthday gift on October 20th, he says his birthday was seven months ago.
Joey tells Ross he doesn't know what "finger quotes" mean, however in the episode The One Where Everybody Finds Out (1999), Joey uses the "finger quotes" to tell Rachel that Monica and Chandler where in the next room "making love".
In 5x14 Joey uses the "finger quotes" to tell Rachel Monica and Chandler in the next room "making love", however in 9x02 Joey tells Ross he doesn't know what "finger quotes" mean.