In the Season 3 finale, Ross enters a room and says hello to an unseen person. In the season premiere, it's revealed he has entered Rachel's room, and in it he finds Rachel spreading Bonnie's bald head with lotion. Bonnie goes to bed. Ross decides to break up with Bonnie to get back together with Rachel, who writes a letter to him. Rachel is willing to reconcile with Ross only on condition that he accepts what the letter says he must. In other words: he has to accept full responsibility for everything that went wrong during their relationship. Ross was too tired to read a 36-page letter in the early hours of dawn ("Eighteen pages - front and back!"). When asked whether he can accept what the letter says, Ross says he "does" and they get back together; however, later when he reads the letter, he realizes he can't accept it and they break up again.
Meanwhile, Chandler and Joey are with Monica at the beach, where she gets stung by a jellyfish. Joey, who saw a feature on the Discovery Channel, suggests peeing on the sting. Monica can't reach, so Joey volunteers. However, he gets stage fright, so Chandler does it. In doing this, he ends his continuous speculations of a relationship with Monica. Despite defining Chandler as a cute, great guy, Monica calls him, "the guy who peed on me." Not long after, Chandler and Joey are robbed in broad daylight after Joey climbs into the cabinet he made and gets locked inside by the thief, who takes almost everything from the apartment. For a while, they fill the apartment with rusty patio furniture and a canoe (The One With The Cat).
Having learned the truth about her birth mother, Phoebe Abbott, Phoebe is extremely disappointed. She storms off, never wanting to see her birth mother again. Abbott tracks her daughter down and starts an uncomfortable, moderately friendly rapport with her daughter. Duing this season, Lisa Kudrow (who plays Phoebe Buffay) became pregnant. It was written into the show as her surrogate pregnancy on behalf of her brother, Frank Jr.and his new wife, Alice Knight.
Joey dates an actress named Kathy, who Chandler has a crush on. Chandler and Kathy fall for each other, sharing a kiss while she is still seeing Joey. Kathy breaks up with Joey, not wanting him to find out about the kiss she shared with Chandler. Chandler's guilt is so great that he buys new furniture for their empty apartment, finally telling Joey about his romantic encounter with Kathy. Joey becomes so angry that he sends off the stuff Chandler bought, until Chandler resolves the issue by spending Thanksgiving in a box (The One With Chandler In A Box). Chandler and Joey make up, and Joey encourages Chandler to date Kathy. After Chandler erroneously accuses Kathy of sleeping with a co-star, she actually does so, and after Chandler finds out, he and Kathy break up.
Thanksgiving this year is awkward for Monica, who invites Dr Timothy Burke, Richard's son, to dinner. She kisses him, a brief lip contact which reminds her of her ex-boyfriend. Monica also starts a catering business with Phoebe, but that partnership ends when Monica accepts a job as head chef at Alessandro's. Monica's subordinates hate her, because she replaced the previous chef that was dearly loved and a family member to many of the kitchen staff. Following Chandler's suggestion, Monica hires then fires Joey in a set-up and gains control of the kitchen.
Monica and Rachel lose their apartment to Joey and Chandler, a result of a bet that they had made. To make matters worse for Rachel, her boss (Joanna) dies. As a result, Rachel is shunted in Personal Shopping atBloomingdale's. Things improve for her in the dating department when she meets Joshua Bergin, who is a customer at Bloomingdale's. Several incidents occur which prevent Rachel from expressing her true feelings to him. In an attempt to meet him at an event he will be attending, Rachel begs Ross to take her boss's neice,Emily Waltham, to Die Fledermaus. Eventually, she starts dating Joshua.
Ross and Emily experience a whirlwind romance, running away to a Vermont bed-and-breakfast the first night they meet, which results in them deciding to get married in London, England. Rachel, in a panic, decides to propose to Joshua. Still in the process of finalizing his divorce, Joshua turns down Rachel's proposal and is eventually scared away after she opens the door to her apartment wearing a wedding dress. Ross sends out the invitations for his London wedding (The One With The Invitation), struggling with the idea of inviting Rachel. He finally decides to invite Rachel, who turns down the invitation due to the fact that she can't bear the thought of seeing Ross marry someone else. She tells Ross that she won't be able to take the time off of work.
The friends, with the exception of Rachel and Phoebe, travel to London to witness their friend's wedding (The One With Ross' Wedding, Part 1). Monica helps Ross with the preparations for his wedding. Due to numerous issues, Emily decides to postpone the wedding. Ross insists that there is no point in postponing the ceremony, not understanding how important a beautiful wedding is to Emily, and the engagement is nearly called off. Monica helps Ross solve the problem by decorating the partially torn-down wedding hall, and the ceremony is back on track.
The rehearsal dinner is a disaster for everyone: Ross can't convince his parents and future in-laws to settle their differences over the wedding finances; Chandler delivers a terrible toast; Joey is homesick, (until he meets one of Emily's bridesmaids); and Monica's mother makes cynical comments, while a drunken guest mistakes Monica for Ross's mother. Monica and Chandler both become depressed, resulting in them sleeping together. And this relationship continues.
Ross' wedding day contains a few surprises: Ross almost catches Monica and Chandler in bed together; Rachel rushes off to London to tell Ross that she still loves him, only to realize that Ross is happy with Emily. However, in the last scene of the season, Ross says "I take thee Rachel" instead of Emily during the ceremony.