Season 9: Episode 208: The Boob Job
Chandler and Monica are a little short on funds, due to Chandler's lack of a paying job. Each individually asks Joey for a loan, swearing him to secrecy. When Chandler notices that Joey recently wrote a large check to Monica, Joey covers by saying it's for breast implants. Phoebe and Mike decide to live together; Phoebe gets excited about the possibilities in their future, including marriage. Then she learns that due to his first failed marriage, Mike never wants to get married again. They decide they want different things, and end their relationship. Rachel buys equipment to baby-proof the apartment, but has to hire a handyman to install it. Then Joey can't get past the baby protection devices.