5x02 "The One with All the Kissing"

Monica and Chandler try to hide their relationship but kiss in front of the others, accidentally. Chandler then kisses Rachel and Phoebe, which Monica then explains as his 'European thing.' Eventually all three girls put a stop to it (this includes Monica). Monica is put in charge of Rachel's love life because Rachel believes that she makes bad decisions, and Phoebe's water breaks and is upset that her bond with the triplets is coming to an end but glad she no longer has to do "pregnant stuff." Rachel tells Ross she is still in love with him, however once she does the two of them realize how ludicrous the situation is and decide not to do anything.