1x19 "The One Where the Monkey Gets Away"

The gang searches frantically for Marcel, who slipped out of the apartment while Rachel was baby-sitting him. Rachel, who does not know that Marcel is an illegal pet, ends up calling Animal Safety. This annoys Ross. The woman who comes to take away Marcel turns out to be an old class-mate of Rachel & Monica. After Marcel is found and safe, Ross finally gets up the courage to try to woo Rachel. But just when it looks like the two might actually spend a romantic evening alone together, Barry, Rachel's ex-fiance, barges into the apartment declaring his love for her.