Season 1: Episode 20: The One With The Evil Orthodontist
Barry (now engaged to Rachel's ex-maid-of-honor) is still pursuing Rachel. She goes to his office to put an end to it and winds up having sex with him. When she tells the gang of her slip, Ross gets really mad at her. Mindy comes to see Rachel and asks her to be her maid-of-honor, then confesses that she was with Barry while Rachel was engaged to him. Rachel tells Mindy she just slept with Barry again, and they both go to Barry's office to break it off, but Mindy winds up remaining engaged to him -- and Rachel is finally sure she did the right thing by not marrying him. Meanwhile, Chandler has a great first date; he calls the woman the next day and leaves a message, then agonizes when she doesn't call back. Finally, she comes by the coffee house and tells him she had his number wrong, but Chandler decides that was the act of a supremely "needy" person and he wants nothing to do with her. Meanwhile, the gang finds (and sort of befriends) a "peeper" with a telescope who watches not only Ugly Naked Guy, but them as well.