S10E5 : The One Where Rachel's Sister Babysits

To help her younger sister, Amy, become a more responsible person, Rachel overrides Ross' strong protests and allows Amy to baby-sit Emma but soon regrets that decision. Meanwhile, Joey volunteers to write a recommendation letter for Monica and Chandler's adoption agency, however, he's concerned about not sounding smart. Also, Phoebe unknowingly thwarts Mike's "anniversary" surprise for her.