8x02 "The One with the Red Sweater"

Rachel won't tell anybody who the father of her baby is until she tells him. Joey tells Monica and Phoebe that a guy slept with Rachel a few weeks earlier, and left a red sweater behind. Phoebe thinks it's Tag Jones and arranges a meeting for Rachel with him. Ross and Chandler attempt to recreate the wedding pictures, after Chandler loses the disposable cameras. Monica opens all of her and Chandler's wedding presents. Monica, Joey and Phoebe find out that Tag is not the father of Rachel's baby, but that it is in fact Ross.