Due to the season number, it has been exactly 7 years (not counting the airdate) since Ross and Rachel's break up in The One with the Morning After (1997).
When Erica is going into labor, Monica has to sit down from freaking out. This is mocking as if she was the one who was pregnant. Courteney Cox was actually pregnant at the time of filming.
In a previous episode (The One Where Chandler Can't Cry (2000)), even when Monica presents a scenario that when she dies and he doesn't cry she will love him anyway. In this episode Chandler is presented as one who'll cry "at the 6 o'clock news"
Last episode to begin with "The One."
At one point, Chandler says "It's like when Melrose Place got cancelled" in regards to Rachel leaving. Melrose Place (1992) was a popular primetime soap opera that ran on Fox from 1992 to 1999. It focused on the lives of a group of young adults living in a brownstone in West Hollywood, California. Matthew Perry had auditioned for the role of Billy Campbell before landing the role of Chandler on Friends (1994).