This is the episode where Ross's jealousy started with Rachel meeting Mark who offers her a job interview. Chandler gets druk and fools around with Joey's sister but he can't remember which one, and when he finds out that it was Mary-Angela he can not recognize her since all of Joey's sisters look alike:).
Joey's Sister: Finally, I thought we'd never be alone. Can I just tell you something, I have not stopped thinking about you since the party.
Chandler: Look, I may have jumped the gun here.Um, I just got out of a relationship and I'm not really in a, in a commitment kind of place.
Joey's Sister: So! Me neither! God, Mary-Angela was right you do have the softest lips.
Chandler: Ahhh, you're not Mary-Angela.
Joey's Sister: No, I'm Mary-Theresa.
Also Phoebe is fooling around with noisy upstairs neighbour...:)