5x15 "The One with the Girl Who Hits Joey"

Ross is initially furious upon learning of Chandler and Monica's relationship, but quickly comes round when he learns it is serious. Joey dates a girl who likes to punch him (Soleil Moon Frye). Ross gets off on the wrong foot with his new neighbors when he, not unreasonably, refuses to contribute towards the retiring superintendent's collection. Chandler and Monica have problems with their relationship after everyone jokes around about marriage. Monica is upset that Chandler refuses to consider getting married one day, and he becomes so worried about losing her that he hastily proposes. Monica turns him down telling him that while she wants him to be open to the idea of getting married one day, they certainly aren't ready yet (much to Chandler's relief).