How did Chandler and Monica became Marafiki in the first place. And what mwaka did they started being Marafiki

How did Chandler and Monica became Marafiki in the first place. Because in thanksgiving 1987 Ross brought Chandler to they house and Monica was still fat and Chandler tall Ross "I don't want to be stuck here with your fat sister" what make Monica lose all her weight and she was upset with Chandler for a year. And what mwaka did Chandler and Monica became Marafiki in.