Monica and Chandler each attempt to write their wedding vows, but both have difficulty. Their friends try to help by reminding them of their pasts together, which we see in the form of flashbacks from previous episodes.
Rachel: Hey, what have you guys been up to?
Ross: Oh, we were helping Chandler write his vows, but he kicked us out because Joey kept making inappropriate suggestions.
Joey: How is, "Monica, I love your sweet ass," inappropriate?
Ross: How's Monica coming along with her vows?
Phoebe: Well, let's just say its she's lucky she has a sweet ass, because she's not so good at the writing.
Ross: I can't believe in four weeks they're gonna be married!
Phoebe: Well let's just hope it works. You know, nine out of ten marriages end in divorce.
Ross: Phoebe, that's not true.
Phoebe: Yeah, you're right. How's the Mrs.?
Ross: Oh man, this is hilarious.
Chandler: Don't worry honey, we'll make yours funnier.
Ross: Dude! How... how did you write this?
Chandler: I stole Monica's and changed the name.
Ross: You can't do that!
Joey: If he goes first he can!