Ross and Emily's London wedding unravels in a series of escalating disasters: the Geller and Waltham parents feud over the wedding bill through the rehearsal dinner and into the ceremony itself, Rachel races across the Atlantic after realizing she still loves Ross, Phoebe fights a losing battle by phone to warn everyone, and Monica — blindsided by a stranger's careless comment — ends up sleeping with Chandler. At the altar, Ross says Rachel's name instead of Emily's, leaving the ceremony in stunned silence and Emily nowhere to be found.

This episode closes out season four by detonating several slow-burning storylines at once. The name slip reframes the entire season's tension around Ross and Rachel, while the Chandler-Monica hookup quietly launches what becomes the show's central relationship going forward. Watching this episode explains wh ...