5x13 - Wedding Bell Blues
Talk about bad timing. The night before Richard and Emily renew their vows, Lorelai and Rory feel obligated to throw Emily a bachelorette party. At the ceremony the following day, Rory tells Logan she wants a relationship with him even though he's not ready to commit. Later, when Lorelai, Luke and Christopher discover Rory and Logan together, half-dressed, the shocking scene leads to an angry confrontation between Luke and Christopher. A furious Lorelai figures out that Emily invited Christopher in an attempt to break up her relationship with Luke.
See you in another life, brother...